Roger Federer reached a ninth Wimbledon semi-final and urged the tournament to let some colour in after enforcing its "too strict" all-white dress code.

The seven-time champion hopes the All England Club can "loosen the grip" on a rule it has tightened and strictly enforced this year, which has led to accusations of players even having their underwear checked before matches.

Former women's world number one Caroline Wozniacki said that was a "pretty creepy" prospect, and it falls at the extreme end of any action that may have been taken.

Where there has been some leeway afforded in previous years, players have been forcefully reminded of the tournament's 10-point clothing and equipment policy during the current fortnight. The rules call for "suitable tennis attire that is almost entirely white".

Federer gave himself the chance to reach another final after taking national bragging rights with a 3-6 7-6 (7/5) 6-4 6-4 victory over Swiss compatriot Stan Wawrinka.

He will abide by the club's dress code when he takes on Milos Raonic in the semi-finals on Friday, not that he likes it.

"We're all white. White, white, full-on white. I think it's very strict," Federer said.

"My personal opinion, I think it's too strict. If you look at the pictures of Edberg, Becker, there was some colours, you know, but it was 'all white'.

"But I respect. I understand. Maybe one day they'll loosen up the grip again a bit, but that's the time we go through right now."

Federer seized charge against Wawrinka once he levelled the contest in their second-set tie-break

Wawrinka, who had been struggling physically, dug deep at the end to save four match points.

But on the fifth Federer followed up a scorching serve, that Wawrinka did well to float back, with a lethal smash from mid-court.

Wawrinka, who at 29 is three years Federer's junior, won the Australian Open at the start of the year and pushed his more illustrious countryman hard.

But Federer has been determined this year to make up for the disappointment of losing to Sergiy Stakhovsky in the second round 12 months ago, and he could atone in the best possible style by landing a record eighth Wimbledon title, going one better than the mark he shares with Pete Sampras.

"There was a lot on the line today playing against Stan," Federer, 32, said.

"I'm really pleased to have come through. Last year was a major disappointment for me because I always see Wimbledon as one of my main goals of the season, side-by-side with rankings and some other highlights that I choose that there are for me.

"I try to be in the best possible shape, so last year was rough. I was very disappointed. I'm happy that one year later I'm back in the semis and with a chance to go further."

While Wawrinka has a rounded game, Raonic brings a more obvious threat: the fierce delivery which has made him the tournament's aces leader with 147 in five matches.

Federer understandably focused in on that big match-winning shot.

"Well, he's got a big serve," Federer said. "Clearly that's what is most visible when you see him play.

"That's the hardest to deal with, I guess. It keeps him in the match. Doesn't matter almost how he plays his return game, he's been serving very well for this entire tournament."