CONCERN has been expressed at the high number of former MPs, including David Cameron and Alex Salmond, who still have access to Westminster.

New figures show that a record 414 former members can still enter the parliamentary estate by means of a so-called “category X” pass, raising fears of potential lobbying and overcrowding.

Among ex-MPs, dubbed “zombie politicians,” on the list are Commons veterans, including not only the former Prime Minister and First Minister but also ex-Labour ministers Jack Straw, Geoff Hoon, and Alan Milburn.

Former ministers Chris Huhne and Jonathan Aitken, who were both jailed, are also pass-holders.

However, some senior figures like George Osborne, the former Chancellor, his old Labour adversary Ed Balls and Nick Clegg, the ex-Deputy Prime Minister, are not.

Ex-MPs who have served at least one full parliamentary term are eligible to apply for a category X pass, which is meant to help smooth a politician’s transition to life outside Parliament.

But Labour’s John Mann insisted the current situation was unsustainable.

The Nottinghamshire MP expressed concern that the category X pass system could lead former members into the temptation to lobby, which is against Westminster rules.

There is no suggestion that anyone on the category X pass list has breached any of Parliament’s rules.

But Mr Mann noted: “It is heading to a crisis because of the refurbishment of Parliament. We are not going to be able to fit in half the people with passes.”

He added: “There has got to be a look at exactly who has got passes for where and why. The current growth in the House is just not sustainable.”

The rise in the number of passes for former parliamentarians comes on top of the current contingent of 650 MPs and more than 800 peers, bringing the total to almost 2,000. Only the National People's Congress of China is a larger legislature with some 3,000 members. Plus at Westminster, there are thousands of MPs' researchers, administrative staff, police and journalists.

A House of Commons spokesman said: “The Former Members' Pass entitles the holder limited access to the Parliamentary Estate unescorted; they may access certain areas for the purpose of meetings and make use of a limited selection of catering facilities during certain hours.

“They may not use any other facilities within Parliament and are forbidden from using their pass in connection with lobbying activity,” he added.