By James Cusick

Opposition parties will tomorrow seek a parliamentary clarification on the Home Office's migrants policy after the new immigration minister, Phil Woolas, signalled a rethink and a call for quotas to be introduced.

The Home Office spent much of Friday and yesterday denying that Woolas had let the cat out the bag and admitted the government was planning a reform of the Australian-style immigration points system.

Woolas was given the immigration portfolio in the recent reshuffle. In a newspaper interview he said getting into the UK had been too easy in the past and was now "going to get harder". He becomes the first government minister to set a limit on the level of Britain's population and linking the upper limit to new immigrants. He said: "This government isn't going to allow the population to go up to 70 million."

Neither Woolas nor the Home Office have offered any detail on how they will keep the population below that figure.

Figures from the Office of National Statistics estimate that the UK's population grew by two million between 2001 and last year. Other ONS projections point to a rise to 77 million by 2051 and to 110 million by 2081.

With immigration from the European Union not controlled by the government as part of EU membership commitments, plus genuine claims for asylum allowed as part of international law set by the UN, both the Conservative and Liberal Democrat front benches want an immediate clarification.

Dominic Grieve, the shadow home secretary, said he wanted a full explanation of how the government were going to deliver on Woolas's new target and whether this was a policy change that the Conservatives had long advocated.

"Talk is not enough," said Grieve, "they must now tell us how they will deliver this."

The Home Office yesterday appeared content to almost contradict their own minister, saying that the current points-based system remained "powerful" and was a "flexible set of controls".

That explanation won't work inside the Commons. With Woolas linking immigration to the rise in unemployment that will come with recession and the economic downturn, the government could also find itself under attack from within its own ranks.

Keith Vaz, chairman of the Commons Home Affairs Committee, said he was "astonished" at a Labour immigration minister "in effect changing the policy".

Keith Best, the chief executive of the Immigration Advisory Service, said Woolas's comment had sent out the wrong message for a modern trading economy.