FORMER Rangers striker Kenny Miller has urged his old club to make a move for Swiss goalkeeper Benjamin Siegrist.

The 30-year-old is a free agent after letting his contract run down at Dundee United after four successful years at Tannadice.

Celtic are said to be weighing up a move for the shot-stopper but with Ibrox No.1 Allan McGregor's future up in the air, the former Scotland internationalist believes the Govan outfit should make the keeper an offer of their own.

"I think it's a good option on a free transfer," Miller told Clyde 1 Superscoreboard.

"I think it was mooted last summer that they [Celtic] were going to go for Siegrist as a potential No.1, and obviously they went and got Joe Hart.

"He has been an outstanding performer in the league for a few seasons now.

"On a free transfer it would be very good business, and we don't know what's going on with McGregor.

"Rangers or a Celtic should be looking at him on a free transfer. Absolutely."

Siegrist would likely serve as understudy to Hart if the goalie opts for a move to Celtic Park but Miller reckons that might not be the worst thing for Siegrist's development.

He explained: "It might be a case that he works with a keeper of his quality [Hart] for a season.

"The one thing when you come to a Rangers or a Celtic from a smaller club in Scotland - a Hearts, a Hibs or a Dundee United - you need to move again.

"You need to move and show you are better than the guys that are already there.

"Unfortunately for a goalkeeper there is only one spot. Maybe Celtic are looking at in terms of a succession plan and they are thinking 'maybe Joe will go at the end of the season'.

"They will want someone in the building, who is capable, and Benjamin Siegrist ticks those boxes."