Gordon Brown set a target last night of deporting 4,000 foreign criminals by the end of the year as a way of easing the prison overcrowding crisis.

The Government is asking prison authorities to begin the deportation process a year before the inmates’ release date, rather than six months as at present.

In an interview with The Sun, the Prime Minister said the Government wanted to double the number of foreign convicts to be removed by December. The previous target was 2,000.

Mr Brown said: “We expect to deport 4,000 foreign nationals who have previously been in our prisons. Two years ago the figure was 1,500 but we are going to take a far tougher line.

“I want a message to go out. If you come here you work and you learn our language. If you commit a crime you will be deported from our country. You play by the rules or you face the consequences. I am not prepared to tolerate a situation where we have people breaking the rules in our country when we cannot act. That will be toughened up.”

Foreign prisoners will not be released early. But by starting the process a year before the release date ministers believe they will drastically cut the number remaining locked up in detention centres while they await deportation.

Mr Brown also confirmed that he is looking for a substantial increase in the time the police can hold terrorist suspects without charge.

In a statement today he will set out a number of options for replacing the current 28-day limit. But he is understood to believe that there are grounds for doubling it to 56 days.

The measure will be at the heart of proposals for a new counter-terrorist Bill to be outlined by the Prime Minister and the Home Secretary today.

Last night Jacqui Smith, the Home Secretary, said that since Parliament last debated the issue there had been new evidence to justify such an extension, with the alleged bombing attempts in London and Glasgow.

Gordon Brown and Ms Smith will announce a series of options for debate, including the case for extending the period of detention before charge, plans to question suspects postcharge and strengthening of control orders. Today’s proposals, in the form of a consultation paper, will also give an update on the review of the use of intercept evidence in trials and will look at other methods, such as the French system of examining magistrates, who supervise the investigation of a case.

Ms Smith told the all-party Home Affairs Select Committee last night that alleged plots were becoming more complex, the international dimension to terror investigations was widening and the security services were now aware of 400 more terror suspects since last November’s figure of 1,600.

“This all gives us a strong view that the time is right to reconsider whether we should allow longer than 28 days for precharge detention,” she said. Her predecessor, John Reid, rejected an extension of the 28-day limit earlier this year, saying that he had not seen evidence to justify it.

But Ms Smith outlined details of recent recent police operations in which six terror suspects had been questioned for 27 or 28 days, after which three were charged. “There is already evidence of us stepping up to the point of 28 days,” she told the committee.

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