Former Celtic striker Pierre van Hooijdonk has said that Brendan Rodgers should be backed in the January transfer market with Rangers posing a serious challenge to their title hopes.

The Premiership champions hold a game in hand on their city rivals and are top of the table on goal difference as the sides prepare to return from their winter break.

Celtic have recruited striker Vakoun Issouf Bayo and brought in PSG's Timothy Weah and West Brom's Oliver Burke on loan. Brendan Rodgers does have other targets  with a deal for Andrew Gutman likely and at least another defender on his wish list. Van Hooijdonk says the squad needs to be bigger to replace players who left last summer and to provide better cover.

"They're still top of the league but I think they realise now that they've really got a competitor with Rangers," the Dutchman said.

"There have been some injuries and also losing some players in the beginning of the season and the question you can ask is 'Did they bring in the players who can step in these boots?'

"The performances dropped. In the last seven years I've never seen Celtic dropping so many points in the first part of the season. Normally they're miles ahead because they won almost everything but this year it wasn't the case."

Van Hooijdonk believes Brendan Rodgers' record, which has seen him win every domestic trophy since joining the club, means he deserves to get the players he needs to remain on top.

He said: "The Old Firm game, if the first half of the season didn't open their eyes, then at least that game would have.

"Celtic weren't playing the strongest possible side but Rangers were all over them.

"One game in hand, still a lot of games to play and you want to have a big quality squad. That will win you titles.

"When the manager is looking for players then you should definitely back him. Especially someone who has done so well for Celtic for some years.

"The 'Ten in a row' always flies somewhere above this city but that's long-term. If you look short-term, if you want to bring in quality players then you have to become champion. and make Champions League because that gives you cash."