David Cameron and George Osborne today insisted that Britain is 'on the right track' as they briefed Cabinet colleagues ahead of a mini-budget expected to be dominated by bleak economic figures.

The Prime Minister and Chancellor told senior ministers that the coalition Government was 'equipping Britain to succeed in the global race', and that everyone must make a contribution towards dealing with the UK's debts 'in a fair way'.

Economic forecasters expect Mr Osborne to be forced to extend austerity by one year, into 2018, today, due to lower than expected growth. And he may also have to ditch his target of putting the UK's national debt on to a downward flightpath by 2015.

Mr Osborne's autumn statement is expected to include some bright moments, with �5 billion for infrastructure spending – including �1 billion to build 10 new schools. And he is widely expected to postpone or scrap a 3p rise in fuel duty pencilled in for January, saving motorists an average �7.69 a month.

But the Office for Budget Responsibility is expected to revise down its GDP growth forecast for 2012 from the 0.8pc it expected in March to around zero, and to slash its 2013 prediction from 2pc to somewhere close to 1pc, giving the Chancellor little leeway for generosity.

Summarising the autumn statement at the end of a Cabinet meeting in 10 Downing Street, the Prime Minister and Chancellor told colleagues its central message was that Britain is 'on the right track' and the Government was dealing with the country's deficit and debts 'in a fair way', said Mr Cameron's official spokesman.

They said that this means 'that everyone must make a contribution and that we are equipping Britain to succeed in the global race', the spokesman added.