RANGERS boss Mark Warburton has told the Ibrox board they must invest in the playing squad this summer - despite his side’s thrilling victory over Celtic in the William Hill Scottish Cup semi-final at Hampden yesterday.

Warburton’s team won a classic encounter against their Glasgow rivals 5-4 on penalties – the first shoot-out between the two sides in a competitive match in history - after they had finished tied 2-2 after 120 minutes to book a place in the final with their fellow Championship club Hibs on May 21.

The Englishman’s players dominated the game for long spells and twice took the lead - through Kenny Miller in the first half and Man of the Match Barrie McKay during the first period of extra-time.

Many Rangers supporters will be confident their team can challenge their Old Firm opponents for the Premiership title next season on the evidence of this impressive performance and morale-boosting result at the National Stadium.

However, Warburton was at pains to stress there is still a large gulf between Celtic and Rangers and further investment would be required – if his side win the Scottish Cup and qualify for the Europa League especially.

Asked if it would be a mistake for Dave King, the Rangers chairman and major shareholder who was at Hampden yesterday and his fellow directors, to think they were at the same level as Celtic as a result of the win, he said: “Absolutely. The gap is there.

“Don’t be fooled by that. The better team won but there is a gap there and we’ve got to recognise that. We cannot go into next season feeling satisfied with second, third or fourth. We need to go into the season to be highly competitive.

“We know that we are 90 minutes from Europe. It impacts on our recruitment as well. I think if we do win the final then we have got to add one or two more players in terms of depth in the squad. So, again, that type of conversation has to go on.

“But we have been making rapid strides. There will be down times, there will be bad days as well, so you have to make sure you are ready for them and try and recruit wisely, get the environment right and keep on pushing forward.

“I don’t want to repeat myself, but it is important now we don’t stop. If Rangers stop we have a problem. We must keep on pushing really hard.

“There is still a gap there, don’t be fooled. We were the better team and the better team won on the day. But Celtic are a team packed with international players. They have European players and we need to recognise that. Nothing has changed from the previous message."

Warburton, who was in the dugout at an Old Firm game for the first time, has admitted he was annoyed by suggestions last week that his Championship side would be blown away by their Premiership opponents.

“I read some outrageous report about how many Celtic would score and how it would be a cricket score,” he said. “Well, hopefully we have shown the gap is a lot narrower than they imagined.

“I’m irritated. The favourites have to be Celtic, absolutely have to be. Anyone that understands football would say they have the stronger squad, they have the experience, they have the financial impetus, they are the favourites. I understand it.

“But I was irritated by people underestimating Rangers. We have been good this season. We have not been clearing the league by 17 or 20 points by chance. We deserve to be. A young squad has come together quickly. So all credit to the players.

“I think they deserved quite a bit more respect. I read reports about them getting battered by Celtic today. Well, they showed today that they have got quality, commitment, work ethic, and that gap is a lot, lot narrower than people are talking about.”

Warburton, who was only able to name five substitutes due to injuries to key players Harry Forrester and Martyn Waghorn and to Billy King and Michael O’Halloran being cup tied, revealed that he had enjoyed the experience of his first Old Firm game.

He also singled out the Rangers supporters for praise for their backing during the match and expressed has delight that they had been rewarded with a win over their city rivals after the difficult spell they have endured.

“You have to enjoy it,” he said. “I was bemused my people saying I’d crumble under the pressure. If you can’t enjoy that then don’t be in the game of football. If you can’t enjoy that you should go and get a paper round. It was magnificent. There was a fantastic atmosphere. You have to enjoy it.

“I enjoyed the whole experience. I just felt that in that cauldron-like atmosphere you knew that was going to come.

“What is most pleasing was that in that type of environment the players never lost focus. To concede two goals after breaks like that you could have crumbled. You could have turned around and said the international players will come and dominate. That wasn’t the case.

“I’m delighted for the fans. Their level of support was magnificent. They’ve been to some dark places in the last four or five years so it’s great they can enjoy days like these. We were down to the bare minimum with just 16 players.

“But we deserved to win the game of football and that’s the most pleasing thing. We dominated the first half and conceded from two breaks. But to show the character to come back was outstanding. We had some young players with the experienced ones and they were first class.

“Now we need to keep moving forward. We’ll enjoy today, but we need to keep moving forward, Rangers cannot afford to stand still.”