Protection of MPs offices from police raids must be reviewed, Commons leader Harriet Harman has said.

The call comes amid continued political fighting over the arrest of senior Tory Damian Green.

Ms Harman said she understood the concerns of MPs over Thursday's raid on the shadow immigration minister's office, saying "big constitutional principles" were at stake.

Mr Green was held for nine hours over alleged leaks of Home Office documents, provoking angry suggestions from MPs of all sides that he was being pursued just for doing his job.

Home Secretary Jacqui Smith dismissed that claim, insisting officers were investigating a "systematic series of leaks" of potentially sensitive Home Office material.

She refused to apologise for the arrest, saying the police had to be allowed to "follow the evidence where they need to" without interference from the Government.

David Cameron has also raised the political stakes over the controversial arrest demanding Gordon Brown denounce the move or face charges of hypocrisy.

The Prime Minister declared that the decision to question Mr Green and search his home and offices was "a matter for the police" of which he had no prior knowledge.

But amid mounting anger and disquiet at Westminster over the action, taken in relation to alleged leaks of sensitive Home Office material, Mr Cameron said the PM had a duty to speak out.

Mr Cameron insisted the arrest was "not about our national security but government embarrassment" and added: "When it comes to vigorous opposition, if this approach had been in place in the 1990s, then Gordon Brown would have spent most of his time under arrest.

"He made his career from passing on Whitehall leaks. And he'll be guilty of hypocrisy if he doesn't speak out.

"The question is: does he think it is right for an MP who has apparently done nothing to breach our national security - and everything to inform the public of information they're entitled to know - to have his home and office searched by a dozen counter-terrorist police officers, his phone, Blackberry and computers confiscated, and to be arrested and held for nine hours?"

Mr Cameron also turned his fire on the Commons authorities for apparently "not thinking twice" about allowing officers to raid his immigration spokesman's office in Parliament.

Speaker Michael Martin has faced calls for his resignation over the matter.

Mr Martin's office has said only that "there is a process to be followed and that was followed" but the Home Office confirmed permission would have been required from the House authorities.

© Independent Television News Limited 2009. All rights reserved.