Officials said the summit did not mark a return to 'beer and sandwiches at No. 10', a phrase synonymous with union influence in the Seventies.

Among those invited was vegetarian Derek Simpson, the leader of Britain's biggest trade union, Unite, which gave the Labour Party 15 million pounds last year.

Simpson told The Independent in comments published Sunday, 'What are the consequences of us not giving Labour money? That will really impair, fatally damage, any chance of Labour winning a general election. We give money to allow the Labour Party to function.'

On Tuesday, Chancellor (finance minister) Alistair Darling warned that 'hard choices on public spending' were necessary once Britain had recovered from the financial crisis.

He said the government 'won't flinch from difficult decisions' but stopped short of announcing what services were likely to be cut.