Jeremy Corbyn has been handed a major victory over Britain’s leading tabloid, after The Sun was ordered to publish a front page correction for a story which falsely claimed the Labour leader only agreed to be initiated as a Privy Councillor because his party stood to gain financially.

The judgement is unusual because critics have accused the recently created Independent Press Standards Organisation (Ipso) of being too feeble to enforce its authority on powerful newspaper firms.

The complaint was made not by Mr Corbyn but a member of the public – a former journalist called Rosie Brocklehurst who worked in the Labour Party press office in the mid-1980s.

The Sun’s front page attacking Labour’s leader Jeremy Corbyn

She objected to a story that published on the front page story of The Sun on 15 September, when there was speculation about whether the recently elected Labour leader would go through the arcane ritual of becoming a privy councillor.

Under the headline – “Labour hypocrite: Leftie who hates the Royals WILL kiss Queen’s hand to grab £6.2m” – the article said, correctly, that Mr Corbyn had decided to join the Privy Council. But it falsely alleged that his sole motive was to secure state funding for the Labour Party.

Under legislation passed 40 years ago, all opposition parties are entitled to what is known as ‘short money’ to pay the salaries of researchers and other aides. The money is allocated according to a fixed formula, which does not depend on whether the party leader is a privy councillor.

The leader of the opposition also receives an extra grant of more than £700,000 to cover office expenses.

When challenged over the 15 September article, The Sun argued that the grant to the leader’s office might be withheld if the leader refused to join the Privy Council – something which has never happened since state funding of opposition parties began. Ipso found the claim was not true. The IPSO Complaints Committee ruled that “it was significantly misleading to claim, as fact, that Labour’s access to Short money (either the £6.2m, or the £777,538.48) was conditional on Mr Corbyn’s joining the Privy Council; the two were not directly connected.”