Parliament says it - and not the government - will make any decision regarding Westminster security, following calls to modernise.
Recent breaches have prompted more visible security at Parliament
In the wake of breaches, both the home secretary and the Commons leader want security for the Palace of Westminster updated to cope with terror threats.
But a Commons spokeswoman said any decision is for "Parliament rather than the Government" or police.
Hunt protesters and an undercover reporter this week breached security.
A Sun reporter smuggled in fake bomb-making equipment and hunt protesters invaded the Commons chamber on Wednesday.
Home secretary David Blunkett told the BBC: "We need to be in the 21st Century in tackling the potential for suicide bombers."
Mr Blunkett's comments echoed Commons leader Peter Hain's calls for a modern outfit to take over the responsibility for security from the serjeant-at-arms.
But a Commons spokeswoman said: "Any decision regarding this is the prerogative of the Speaker Michael Martin and other appropriate parliamentary
bodies acting on behalf of the House of Commons, together with the Lord Chairman of Committees in the Lords.
"It is a decision for Parliament rather than the Government, police or
Speaking on BBC Breakfast Mr Blunkett earlier said: "I'm in charge of security for the nation as a whole and what's happened here undermines confidence in the security service and counter-terrorism branch who, like me, have absolutely no control over the decisions of the House of Commons and the House of Lords.
"And what Peter Hain, the Leader of the House, has been saying I support,
which is that we now need not medievalism but modernity."
Mr Hain said the newspaper's undercover stunt, which came a day after hunt protesters halted the debate on the Hunting Bill, confirmed his worst fears about security in Parliament.
He told BBC Radio 4's Today Programme that he had been approached last summer by the security services who "had, for some months, been seeking to persuade the authorities in the House of Commons to be much more vigilant about security and update their procedures".
He added: "They had intelligence that was extremely disturbing.
"They briefed me some time ago about intelligence they had about al-Qaeda operatives in Britain focusing on Parliament."
The "horrifying reality" was that peaceful protesters - such as the anti-hunt intruders - could have been suicide bombers, Mr Hain warned.
He said he wanted a central director of security - "a modern professional with up-to-date knowledge of terrorist procedures and security matters" - to oversee the protection of Parliament, taking over responsibility from the serjeant-at-arms and his staff.
One pro-hunt protester, David Redvers, said they had no inside help, adding that it was "frighteningly simple" to gain entry to the Commons.
The eight protesters who tried to barge into the Commons chamber at Westminster have now been released on police bail.
The Sun newspaper said its journalist had been working for 11 days in the catering department at Westminster.
Sun managing editor Graham Dudman said the stunt had exposed "very serious" failings in security at the Commons.
Mr Dudman said reporter Anthony France was able to get a job as a waiter using false references - which were not checked in any way but "couldn't have been more bogus".
The materials he smuggled in the midst of heightened security on Thursday included batteries, wire, a timer and modelling clay.
Photographs of the reporter show him serving tea to Deputy Prime Minister John Prescott while at Westminster.
Both the Tories and Liberal Democrats have called for a radical overhaul of Parliamentary security.