Senior MPs and peers, including a string of ministers, have given virtually unfettered access to Parliament to spouses involved in lobbying for companies and campaign groups, a Telegraph investigation can reveal.

Karen Bradley, the Northern Ireland Secretary, and Sir Kevin Barron, the chairman of the Commons sleaze watchdog, are among a series of parliamentarians whose partners hold “spouse passes” entitling them to around-the-clock access to the Palace of Westminster despite their work for organisations that lobby MPs and ministers over policies and funding.

Mrs Bradley’s husband Neil is listed in the European Commission’s register of lobbyists as “group manager government affairs” at International Airlines Group, the owner of British Airways, while Lady Deane-Barron, an independent “government affairs consultant” until 2012, now works on “advocacy” at the YMCA charity.

In another case, Paul Kenward, who as managing director of British Sugar campaigned against tax on fizzy drinks, holds a pass sponsored by Victoria Atkins, his wife and the crime minister.

Meanwhile, Robin Walker, a Brexit minister, sponsors a pass for his wife Charlotte Keenan, who, while not involved in lobbying, is a senior executive at Goldman Sachs, which campaigned against Brexit.

The passes give partners access to a vast swathe of Parliament, including restaurants and bars, and allow them to bring up to six guests. They are intended to allow parliamentarians to see their partners and children with ease.