Over a third of broadband customers said they have an internet connection which frequently drops out, a survey from Which? revealed.
According to the consumer group:
- One in seven have not been able to connect to the internet at all on more than one occasion.
- Of the 45% experiencing slow speeds, 58% said this was a frequent or constant problem.
- Poor customer service was also exposed by the survey - Around one quarter (27%) have waited more than two days for after reporting a loss for anything to be done.
- Some 11% waited a week or more.
- The watchdog found 31% who contacted their provider with a problem did not get a resolution at all.
Broadband companies have been accused of charging some customers for speeds they are not able to get, with nearly half of people suffering from a slow connection, according to a consumer group.
Which? found 63% of the 2,012 broadband users quizzed experienced problems with their internet and 45% suffer through slow download speeds.
They are calling on providers to give their customers "the speed and service they pay for".
Which? executive director Richard Lloyd said: "The internet is an essential part of modern life, yet millions of us are getting frustratingly slow speeds and having to wait days to get reconnected when things go wrong.
"It's less superfast broadband, more super slow service from companies who are expecting people to pay for speeds they may never get."
Nearly two-thirds (62%) of those questioned said they have no idea how much internet data they actually use as part of entertainment bundles they pay for, while almost a third of respondents (29%) do not know what capacity they are paying for.
Although an increasing number of consumers are putting their hands in their pockets to pay for additional online streaming services, there is still a considerable amount of cash wasted on paid-for TV channels which go unwatched.
People should regularly assess their viewing habits to ensure they are getting value for money from their TV service.
The cost of TV "wastage" - the amount spent on paid-for channels that are going unwatched - has decreased since last year.
With the cost of TV entertainment within a bundle averaging at £22 per month in 2014, households are spending £195.35 annually on unwatched TV channels.
The report was issued by the Post Office and Freeview.
The amount households spend on entertainment bundles has increased to record levels, a national review of internet users' spending habits has shown.
Vision and Value 2014 - an examination of television, broadband and home phone usage among consumers who choose to bundle the services - found that monthly spending on bundles has increased since 2013, costing each household an average of £50 per month.
This equates to an overall national spend of £3.3 billion - the highest it has ever been.
The report also found that almost one in five UK bundle users is spending an additional £10 per month for online TV subscriptions.
The Government has dodged suggestions more needs to be done to support families living in rural areas by installing better broadband connection.
Communications Minister Ed Vaizey defended the Government's plans to install superfast broadband to "95% of the UK by 2017".
Government knows how vital broadband can be to people's daily lives and what an important role it plays in education, from schoolchildren being able to do their homework to accessing information.
We are making sure that thousands of people across the country, particularly in rural areas, are getting access to superfast broadband.
We are well on track to deliver superfast broadband to 95% of the UK by 2017.
Some 20% of families reliant on the internet for their children's education have found they cannot access online resources because of poor broadband connection, a report has found.
Research carried out by insurers NFU Mutual found one in five of 1,600 parents quizzed were having to make more phone calls because of poor broadband connection.
Tim Price, rural affairs specialist for NFU Mutual, said: "As more educational resources become internet-based, country children risk falling behind their urban counterparts.
"Studying via the internet is now a key part of children's education and it's unfair that learning opportunities are being affected by slow internet speeds."
The announcement of small business grants for high speed broadband coincides with the Small Business Saturday initiative promoting the firms Mr Cameron described as the "lifeblood of our economy".
Up to £3,000 of broadband vouchers for small business in these cities is not only a massive boost for growth in the UK, but also has the potential to bring China to Cardiff, Brazil to Bristol and the Emirates to Edinburgh in an increased export market.
To do that we are working on a complete overhaul of the UK's infrastructure; high speed broadband is a vital part of this. And on Small Business Saturday, what better way to support small businesses - the lifeblood of our economy - than to help kit them out for the 21st century.
Small businesses in 10 cities across the UK will be able to apply for grants to install high speed broadband as part of a £100 million scheme to boost growth and exports.
Firms in Belfast, Salford, Portsmouth, Cardiff, Derby, Bristol, Edinburgh, Newport, London and Manchester will be able to access grants worth up to £3,000 to improve their connections, with the scheme due to be extended to 12 more cities next year.
Prime Minister David Cameron said he wanted to give firms the ability to set up or locate anywhere in the UK.
Network Rail is to roll out "high speed mobile broadband" across the country's busiest lines, Transport Secretary Patrick McLoughlin has announced.
The plans will be industry funded, and if successful will make it feasible for passengers to watch streamed videos on their mobiles.
70% of passengers should have access to the faster internet by 2019, according to the Department for Transport.
The move was announced at the Conservative party conference in Manchester.
A BT spokeswoman said the company was "disturbed" by an MPs' report that claimed the government's rural broadband scheme was mismanaged and left the internet provider with a near monopoly.
We are disturbed by today's report, which we believe is simply wrong and fails to take on board a point-by-point correction we sent to the committee several weeks ago.
We have been transparent from the start and willing to invest when others have not.
It is therefore mystifying that we are being criticised for accepting onerous terms in exchange for public subsidy - terms which drove others away.
The taxpayer is undoubtedly getting value for money.
BT faces a payback period of around 15 years on its rural broadband investments in spite of the subsidies available.
The DCMS (Department for Culture, Media and Sport) has imposed a rigorous auditing process that ensures every penny is accounted for.