The former minister was patted on the back by Tory colleagues, but senior members of the Commons privileges committee said it could mean that MPs would lose some of the protection of privilege.
"If information is submitted under privilege and is confidential, it could now be open to MPs to produce it in court to defend a libel action. This opens it up," said one senior source.
In a vote split mainly down party lines, Mr Hamilton's Tory colleagues turned out in strength to vote 264 to 201 in favour of amending the 1689 Bill of Rights to enable him to pursue the libel action over allegations about his stay at the Ritz Hotel, Paris, owned by Mohamed al-Fayed.
Mr Hamilton's victory will enable him to continue in the Autumn a libel action against The Guardian, which failed after the defence successfully argued that they were unable to mount a proper defence because the Bill of Rights prevented the courts discussing proceedings in Parliament.
The privilege was given to MPs to ensure their freedom of speech in Parliament.
Last night's vote, supporting an earlier change to the Defamation Bill in the House of Lords, will allow Mr Hamilton to return to the court when it becomes an act, and waive the privilege.
MPs feared that without the change in the law, they could not successfully sue newspapers for libel for any case involving proceedings in Parliament.Reuse content