Tories face a backlash after an online ad hailed bingo and beer tax cuts as "helping hardworking people do more of the things they enjoy".
The Scottish Parliament could gain more power over tax if voters reject independence, David Cameron has suggested.
MP Peter Bone insists he is "totally innocent" of allegations of benefit fraud, after his home was raided by police.
Culture Secretary Maria Miller is facing a potentially decisive day in her battle to keep her job amid a row over her expenses.
David Cameron is likely to be questioned about Mrs Miller in Prime Minister's Questions this lunchtime and then Tory backbenchers will have a chance to voice their concerns at a meeting of the party's influential 1922 committee.
The Culture Secretary issued another apology last night, admitting she "let people down" in the way she approached the probe into her accommodation expenses, amid signs that support from her colleagues is ebbing away.
Labour's lead in the opinion polls has been cut to a single point in a sign Ed Miliband's party has lost ground since the Budget.
The Opinium survey for the Observer places Labour on 33%, a slide of two points from a fortnight ago, and the Tories on 32%, after a gain of two points.
The poll puts Ukip down a point on 15% while the Liberal Democrats are unchanged on 10%.
The online survey was of 1,936 British adults between March 25 and 28, around a week after the Budget was announced by George Osborne.
Conservative MP Peter Bone and his wife will not face any charges over fraud allegations, the Crown Prosecution Service has announced.
Northamptonshire police investigated the Wellingborough MP and his wife over claims that assets belonging to his mother-in-law were concealed so Northamptonshire County Council would fund her care home fees.
The CPS said: "We have decided there is insufficient evidence to charge any criminal offence."
It explained: “The evidence showed: firstly that the woman’s mother considered the suspects' conduct to be acceptable; secondly that the suspects acted openly in declaring the sale of the mother’s house to the Council; thirdly that no element of dishonesty could be proved."
It added that there is an ongoing civil litigation case.
The Conservative Party chairman Grant Shapps has hit back at criticism of an advert he tweeted celebrating the cuts in bingo tax and beer duty.
The party advert said the measures were "to help hardworking people do more of the things they enjoy". The Tories and Mr Shapps were accused of being "condescending" by Labour and the Lib Dems.
On a trip to Carlisle, he told BBC Radio Cumbria: "We can all argue about whether the word should be 'they' or 'us' or whatever.
"Personally, I drink beer and I love a game of bingo so I can't see why on earth they think this is more important than talking the long-term economic future of our country, supporting actually sectors like bingo or the local pubs."
Sources close to Boris Johnson say the Mayor of London is still undecided as to whether to run as a Conservative candidate at the General Election next year.
The Deputy Prime Minister Nick Clegg has dismissed David Cameron's appeal for Boris Johnson to become an MP again as the latest storyline in a "Conservative Party soap opera" that is "very difficult to follow".
Mr Cameron's comments have refueled speculation that Mr Johnson may bid for a return to Parliament at the General Election next year.
The Liberal Democrat leader said while his fellow Coalition leaders and the Mayor of London spent time sorting out "who's doing what in the Conservative Party" he would carry on "concentrating on completing the economic recovery as fairly as possible".
David Cameron has made a plea for Boris Johnson to return to Parliament and join the Conservative Party election campaign in Westminster.
In an interview with James Corden, who was guest editing The Sun for Sport Relief, the Prime Minister said he thought the Mayor of London was "great", and said "there is nothing ignoble about wanting my job":
I want him to get back in Parliament. I think he's great.
It's a bit like football - if you have got a great striker you want him on the pitch.
It's up to him. He can complete as Mayor, or he can stay on as Mayor and come back to the House. I want him on the team
The Conservatives' online Budget ad has been described by Ed Balls as "patronising and embarrassing".
The Shadow Chancellor held a printout of the online-only poster in the House of Commons as he said it poster showed the Tories were "out of touch".
One Twitter user came up with a new way of spoofing yesterday's Budget, following measures aimed to please beer drinkers and bingo-goers.
Nick Clegg has described the Conservatives' online Budget advert as "silly" but denied that George Osborne's statement marked a "Budget for plebs".
"It was a coalition budget through and through," the deputy prime minister told a caller on his regular LBC radio phone-in.
"I am really very proud of all of it," he added.