Voters will go to the polls on Thursday
Campaigning for the European and English council elections is in its final stages - as events at Westminster continue to overshadow it.
Tory leader David Cameron said the government was "collapsing before our eyes" while Lib Dem leader Nick Clegg said there was "no-one in charge".
This followed the resignation of Communities Secretary Hazel Blears.
But Mr Brown said he was focused on tackling the big issues, such as reform of Parliament and the recession.
The final day of campaigning before Thursday's elections has been overshadowed by apparent turmoil within the government, after a series of ministerial resignations.
At prime minister's questions, Mr Brown rejected suggestions that he had lost control over his cabinet after Ms Blears' departure and that of Home Secretary Jacqui Smith.
"The government is collapsing before our eyes," Mr Cameron said, reiterating his call for a general election.
The Tory leader accused Mr Brown of having "no confidence" in Chancellor Alistair Darling, also criticised for his expenses claims.
Mr Brown said his chancellor was "doing a very good job" but refused to be drawn on whether he would be keeping his job in a reshuffle expected after Thursday's elections.
Mr Brown said there was "work to be done every day" to deal with the recession and the government had taken action to nationalise the banks, help small businesses and people who were losing their jobs.
"This is the action that needs a government that is taking action every day," he said.
He said the Tories had no answers or policies on the big issues of parliamentary reform and the economy.
"That is no basis on which to hold a general election," he told Mr Cameron.
Addressing Conservative activists in Hammersmith, west London later, Mr Cameron joked that he could not stay longer because "if you stay out of Westminster too long, by the time I get back another minister has resigned".
He told campaigners: "We have just got one day to go before these vital elections, these are the biggest and the most important set of elections until the general election ... that general election cannot come a moment too soon."
For the Lib Dems, Mr Clegg said the government was "paralysed by indecision and crippled by infighting".
He told Mr Brown: "The country doesn't have a government, it has a void. Labour is finished. The only choice now is between the Conservatives and the Liberal Democrats."
The SNP, which with Plaid Cymru has called for an immediate dissolution of parliament, said the cabinet was in open revolt.
Mike Weir said the country was witnessing the "pathetic sight of a cabinet attempting to reshuffle itself" and demanded an immediate general election.
'Struck a chord'
UK Independence Party leader Nigel Farage says he expects to double his number of MEPs.
Mr Farage, whose party has nine MEPs and beat the Lib Dems into fourth place in the 2004 European elections, hopes to beat them again and also come ahead of Labour this time.
He said UKIP's view that the UK should leave the EU in favour of a free trade deal was now supported by a "clear settled majority" of British people.
"We're putting pressure on the system at Westminster and if we do spectacularly well, if we cause an earthquake in British politics this Thursday, then the big party leaders have to listen."
The Greens, who have two MEPS, say they are on course for their best-ever European result, with party leader Caroline Lucas saying their call for a million new "green" jobs has "struck a chord" with people.
A YouGov online survey of 2,072 people published on Tuesday suggests the turnout for the European elections could be much higher than usual.
It suggests 50% of the electorate plan to vote on Thursday - turnout in 2004 was 38%.
Other smaller parties are also hoping to benefit from voters' anger with the main parties over expenses.
Among them is the British National Party who are hoping to boost their 2004 vote enough to get their first elected representatives in Brussels.