Ofgem chief executive Andrew Wright said the reforms on fixed term deals will make the energy market "simpler, clear and fairer" and make it easier for consumers to "vote with their feet".
Mr Wright said in a statement:
In an era of rising prices it is vital that competition works as effectively as possible.
Our reforms seek to give consumers the tools they need to find the best energy deal for them and to ensure that suppliers have to treat them fairly.
Now we are looking for energy suppliers to pick up the baton and put their efforts into restoring consumer trust.
Ofgem said its new rules on fixed term energy deals will give consumers more protection so they have certainty the price and conditions they signed up to will not be altered.
The energy regulator said consumers will not be rolled-over to a new fixed term deal once their contract has ended, "but to a tariff which allows them to switch away without penalty".
Customers will also get over 40 days warning that their fixed deal is coming to an end so they have plenty of opportunity to compare the market and find the best deal for them.
Energy regulator Ofgem has introduced tougher rules on fixed term contracts.
The new rules, which come into force today, include:
- Fixed means fixed - customers on fixed term tariffs are given certainty on price
- Automatic roll-overs on to another fixed term deal when a contract ends are banned
Ofgem believes these reforms will lead to simpler energy tariffs from the end of December.