Celtic's chairman said a review of manager Neil Lennon's position was ongoing as the Glasgow giants on Monday revealed the financial cost of playing behind closed doors due to coronavirus restrictions.

The Scottish champions revealed a 24 percent fall in revenue for the six months to December 31 from £53.3 million ($74 million) to £40.7 million.

That resulted in a pre-tax loss of almost £6 million as, unlike in previous years, Celtic did not sell one of their prized assets in the transfer market last summer.

The Hoops hierarchy had prioritised trying to win a record 10th consecutive league title, but that plan has backfired with Lennon's men 18 points adrift of Rangers at the top.

"The two key factors that adversely affected our financial results for the period under review were: firstly, reduced gains from player trading as we sought to keep intact our squad this season; and, secondly, the unforeseen and prolonged value destructive impact of Covid-19," chairman Ian Bankier said.

"Our strategy for season 2020/21 was to invest in the team and to retain our best players, with the objective of delivering the league championship."

Pressure from supporters has been mounting on the Celtic board to sack Lennon as there has been little improvement in performances since a review into his performance was publicly announced in early December.

However, Bankier defended the decision to not act more swiftly to save Celtic's season.

"I must state clearly that all decisions we take will be taken calmly and rationally. We will not make hasty decisions that we might regret," he said in a letter to supporters.

Celtic still have a game in hand on Rangers and face their local rivals twice more this season to try and cut the gap.

However, Steven Gerrard's men have not lost a league game all season and need to win just four of their remaining nine matches to claim a long-awaited title.