The reasons behind two controversial peerages awarded by Boris Johnson have been published after an 18-month freedom of information battle.

Baroness Owen of Alderley Edge and Lord Kempsell, two former special advisers in the Conservative government, were appointed to the House of Lords in Mr Johnson’s resignation honours list.

Both appointments were subject to criticism from the ex-prime minister’s political opponents, as well as transparency campaigners who called for the reasoning behind the appointments to be revealed.

Martin Rosenbaum, a journalist and freedom of information campaigner, took the House of Lords Appointments Commission (Holac) to a first-tier tribunal in order to reveal who had written letters of citation for the two Tory peers.

Holac initially refused Mr Rosenbaum’s freedom of information request to reveal the citations for Lord Kempsell and Lady Owen on the grounds they contained confidential personal information.

Holac told the tribunal there was a “strong public interest in protecting the confidentiality of the consideration of individual nominees and ensuring the potentially sensitive vetting information can be candidly assessed”.

But the tribunal upheld Mr Rosenbaum’s arguments that releasing the information was in the public interest.

Citations for Lord Kempsell and Lady Owen recount their career histories at the heart of Mr Johnson’s government, including during the pandemic.

Lady Owen led on “many sensitive and key projects including advising the prime minister and the chief whip on suitability for ministerial appointments during the reshuffle”, one of her citations said.

While much of the information remains redacted, Conservative former ministers Grant Shapps and Chris Heaton-Harris were revealed as nominees for Lady Owen.

Speaking after the tribunal’s judgment, Mr Rosenbaum said: “The reasons cited for nominating Owen to membership of the House of Lords do come across as very thin, inadequate and lacking in evidence of relevant achievements.

“They leave her peerage as a mystery rather than properly justifying and explaining it.

“I am very pleased that the documentation has now been revealed, but it shouldn’t need an argument over 18 months for the public to find out what reasons are officially provided for allocating certain people important political powers.

“Members of the House of Lords debate and vote on laws that control the British public’s lives. As a basic principle the public is fully entitled to know what reasons are given for why they have been appointed to rule over us.”

Lady Owen and Lord Kempsell have been contacted for comment.