Labour leadership contender Ed Miliband has challenged Liberal Democrats in the coalition Government to stick to their principles and vote against George Osborne's Budget.
"This is a week of judgment for the Liberal Democrats," Mr Miliband said during a visit to Brussels.
"We will see tomorrow what the Budget looks like but I think a lot of Liberal Democrat voters are feeling very unsettled about what the Lib Dems are going along with."
Mr Miliband, on a day trip to canvas for leadership votes amongst Labour's Euro-MPs, said it would be wrong to support the Tory Budget just to prop up the coalition:
"I say to the Lib-Dems very clearly that they should exercise their consciences and be willing to oppose this Budget, on issues such as VAT and fairness.
"If not, they will be massively betraying their people and they have a real duty to their people who, in Europe and in Britain will expect them to judge this Budget on what it does , and not simply to go along with it".
Mr Miliband is in Brussels seeking the backing of as many of the 13 Labour MEPs as possible for his candidacy as Labour leader.
He claimed the certain support of at least two - Arlene McCarthy (North West) and Linda McAvan (Yorkshire and the Humber) - and spent the day in talks with others on Labour's future approach to the EU.
"Our relationship with the EU needs a re-think. We must take a much more pro-European stance" he said.
"We need to have less fear about some of the things Europe does, such as legislation on part-time workers and agency workers."