Unemployment has been rising steadily despite economic growth

The prime minister signalled that the fall would be shown in official statistics being released on Wednesday.

The most recent figures said the number of people out of work rose by 92,000 to 1.68 million between April and June.

The Tories and Lib Dems are accusing Mr Blair of breaking protocol by trailing official figures in advance.

The number claiming unemployment benefit rose by 2,000 to 957,000 in July, according to figures from the Office for National Statistics (ONS) published last month.

But Mr Blair told TUC delegates: "The flexibility of our labour market on the whole has been a plus for this country, which is one reason why we've got such low levels of unemployment, compared with other countries.

"And tomorrow I think we will probably see - for the first time in some months - a fall again in unemployment, which is very, very welcome indeed."

'Irresponsible gaffe'

His words came as he faced criticism for job losses in manufacturing, which has borne the brunt of the losses.

The Tories accused Mr Blair of making an "irresponsible gaffe".

Shadow chancellor George Osborne, said: "Important economic data should not be blurted out at meetings with trade unionists.

"This proves why we need independent statistics that are not subject to ministerial spin. Last year Gordon Brown promised that would happen. But he has failed to deliver."

And Lib Dem Treasury spokesman Vince Cable said: "This suggests a certain naivety on economic policy matters. Employment data is market sensitive, it should be released to the market in a proper manner in agreement with the Treasury.

"It does suggest some rather surprising information, since unemployment has now been rising for 15 months. But if there is a genuine change in trend, it should have been released in the correct way."