Ed Miliband has said Labour would govern for the whole country "not just for the wealthy few" as he launched Labour's English local elections campaign.
The Opposition leader used a meeting of activists in Birmingham to rally his troops following last week's shock by-election defeat at the hands of George Galloway.
He faces a crucial test of support on May 3 - with elections in England, Scotland and Wales - and goes into the campaign with healthy national opinion poll leads over the Tories.
Miliband launches poll campaign
With the Government enduring a fraught period amid controversy over a top rate tax, panic buying at the petrol pumps and cash-for-access claims, he would hope to score well at the ballot box.
However the shock Bradford result - where Respect's Mr Galloway won by 10,000 votes, overturning a 5,000 majority - threw a question mark over the strength of support for the party.
In a speech Mr Miliband said: "Labour is changing so that we can change the country."
He went on: "This Government has abandoned the pretence that they can govern for the whole country.
"They have betrayed middle Britain. They are spending their time listening to their donors, the people who give millions of pounds to the Conservative Party, cutting taxes for millionaires, not the millions of people of this country.
"We are determined to govern for the whole country, not just the wealthy few. They are the values that the people of Britain demand."
Seeking to capitalise on the unpopularity of last month's Budget, he said: "We wouldn't be cutting the 50p tax rate for millionaires, we would actually be spending the money to make sure those pensioners' tax allowances were put back in place."