Celtic are on course for an eighth successive title win, while a Scottish Cup final victory would make it three domestic trebles in a row.

Rangers are second with five games to go, having finished third last year.

"It is extremely gratifying to have witnessed the progress that has been made over the last year," said King.

Steven Gerrard's first season in management brought a run to the Europa League group stage from the first qualifying round, while a winless sequence of 12 games against Celtic was ended at Ibrox in December.

However, despite being the league's top scorers, Rangers have won 19 of their 33 outings, compared to Celtic's 24 victories, and trail the reigning champions by 11 points.

"Much of the progress on the pitch can be attributed to Mark Allen (director of football), Steven Gerrard and their respective management teams," said King in an online letter announcing a five per cent increase in season ticket prices.

"Turning to a young manager was a risk but it was one that Mark and the board felt we should take because of Steven Gerrard's football pedigree. Steven's passion, professionalism and winning mentality has been inculcated throughout the football activities at all levels and we have seen strong benefits from this."

Former Liverpool captain Gerrard signed 15 players last summer and strengthened his squad further in January by recruiting Jermain Defoe, Steven Davis and Glen Kamara.

"We saw periods where we were rightly regarded as title contenders, followed by periods of varying quality," added King.

"Despite these periods of inconsistency it is clear that the playing squad is significantly stronger than in recent seasons and, importantly for future transfer activity, the overall value of the squad has greatly increased."

On the season ticket prices, King said "we feel this is not an excessive increase", adding that all revenue will "solely go towards the first-team squad".

'It is going to take four players'

Former Rangers manager Ally McCoist says he feels his old club are "three or four players away" from challenging Celtic.

"Fans to a certain degree, don't want to be within reach, they want to be alongside Celtic, serious about challenging at the top of the league, winning cups, and it is going to take four players for them to do that," he said.

"Rangers need to get four top, top players who are going to go into the team and play.

"And I might be changing my mind on that if you are selling a couple.

"Whether they take the money for Alfredo Morelos, take the money for James Tavernier and reinvest it but I think they are three or four players away."