Remarks made in the Chamber of either House of Parliament have been protected by parliamentary privilege - so you cannot sue for defamation if an MP has made his remarks in the House of Commons (this doesn't apply to remarks made by MPs outside). This is an ancient right, now in Statute as a result of the Bill of Rights 1689 [Article 9 - That the Freedome of Speech and Debates or Proceedings in Parlyament ought not to be impeached or questioned in any Court or Place out of Parlyament.]
Reporting these remarks has been regarded as attracting qualified privilege - not actionable unless malice can be proved.
In the House of Commons, Business Questions, the issue was raised by Theresa May
The website TheyWorkForYou.com has been threatened with legal action for repeating what was printed in Hansard. Will the Leader of the House make a statement about the application of parliamentary privilege to organisations with a licence to reprint Hansard?
The Leader of the House responded
To deal with the serious point that the right hon. Lady made at the beginning of her remarks, I gather that there was a report that the website, TheyWorkForYou.com, is being sued for defamation for repeating what was printed in Hansard. I am grateful to the right hon. Lady for giving me notice of the issue. The position is made very clear and is spelled out in “Erskine May”, which says that “the publication, whether by order of the House or not, of a fair and accurate account of a debate in either House is protected by the same principle as that which protects fair reports of proceedings in courts of justice...This is a matter of common law, rather than of parliamentary privilege.”
The matter is privileged, and we will obviously watch that action with great care, but our democracy could not work if fair and accurate reports of our proceedings were subject to attack from people moving defamation proceedings."