Cabinet Secretary Simon Case and Government ethics chief Darren Tierney have been blocked from giving evidence about Downing Street parties before a parliamentary committee.

The pair were due to give evidence as part of the Public Administration and Constitutional Affairs Committee’s inquiry into the propriety of governance in the wake of Greensill.

The hearing was confirmed several weeks ago, and it was due to discuss the Downing Street parties, as well as the management of conflicts of interest and unregulated appointments in the civil service, and the proposed cuts to the civil service of 100,000 jobs.

However, the committee was then told that ministerial approval for the pair to appear had been pulled. The hearing has now been rescheduled to June 28.

The intervention to pull the session at such short notice evades timely parliamentary scrutiny of these plans and puts Government transparency in a poor light

Committee chair William Wragg said the decision to pull the hearing at short notice “puts Government transparency in poor light”.

“The session with the Cabinet Secretary was an important one considering the number of propriety and ethics issues on the agenda”, he said.

“We had also hoped to get clarity on the Government’s plans for civil service reform, public scrutiny of which was much needed after they were briefed to the press last weekend.

“The intervention to pull the session at such short notice evades timely parliamentary scrutiny of these plans and puts Government transparency in a poor light.”

Mr Case had to remove himself from the inquiry into the parties – to be replaced by Sue Gray – after reports emerged of a gathering in the Cabinet Office.

It was reported the do had been organised by a private secretary in Mr Case’s team, and that it was included in digital calendars as: “Christmas party!” and included an online quiz.

The Cabinet Office said Mr Case played no part in the event, “but walked through the team’s office on the way to his own office”, and he avoided receiving a fine.