Pakistan's captain, Younis Khan, has expressed his exasperation at the allegations of ball-tampering that marred his team's crushing victory over New Zealand at Lord's on Saturday, and has called upon his critics to produce TV evidence of any alleged misdemeanours, rather than resort to innuendo.

Speaking in the aftermath of the 39-run victory over Ireland at The Oval that sealed Pakistan's progression to the semi-finals, Younis defended his star bowler, Umar Gul, who followed up his figures of 5 for 6 at Lord's with another superb spell of 2 for 19, and hit back at the comments made by New Zealand's captain, Daniel Vettori, who claimed after the Lord's defeat that he had never seen any bowler achieve reverse-swing as early as the 12th over of an international fixture.

"Everyone has his own opinion, especially when you get out cheaply and lose a game like that because New Zealand have a big reputation in world cricket," said Younis. "But for reverse swing you need pace and a good action, and Gul has a good action. It is an art, it is not cheating, and Umar knows the art, especially in Twenty20s. In every single game he performs like that."

Vettori confirmed that he had "raised a couple of concerns" with the on-field umpires and the match referee, Ranjan Madugalle, after Gul had claimed the first five-wicket haul in Twenty20 internationals to dismiss New Zealand for 99, but he later added that he had put the matter behind him after the officials had "no issues at all with the state of the ball".

"The amount of reverse swing that we saw was new to us and therefore we raised a couple of concerns," Vettori said. "They relayed back to us that they had no issues at all with the state of the ball. We accepted that and now we move on to our important game against Sri Lanka." Vettori also said he had no discussions with Younis after the game regarding the matter.

Younis, however, maintained that the roughed-up condition of the ball had been due to the hard hitting in Twenty20 cricket, and was not impressed that the matter had been allowed to escalate, especially given how damaging Pakistan's last ball-tampering row, again at The Oval back in August 2006, had turned out to be. On that occasion, the team, captained by Inzamam-ul-Haq, had refused to retake the field after being docked five runs by umpire Darrell Hair, and went on to complete the first forfeiture in the history of Test cricket.

"We are not cheating, but today was very embarrassing," said Younis. "All the time the umpires were checking the ball, and there are plenty of cameras, so how could we cheat? It's not good. And every time it is happening in England. Why? We have good actions and we have pace. So don't disrupt a boy like Umar Gul, he has a good reputation.

"And don't embarrass a team like Pakistan, we already have a lot of controversies in the whole world, and we are suffering a lot of things. Forget these things and focus on the game. Let the cameras catch it if anything is happening with the ball. In this game a lot of sixes are hit, and the ball goes in the crowd, and hits the concrete."

The Pakistan board and team management also expressed their disappointment that questions were being asked about Gul's reverse swing. Coach Intikhab Alam said it was down to Gul's talent. "It is disappointing to hear these things," Intikhab told AFP. "Umar is a fantastic bowler. Not everyone can bowl a reverse ball. You've got to have a special ability to do that. He's quick and his action makes a lot of difference."

Younis agreed with that assessment. "He does his hard work, and like Imran Khan, Wasim Akram, Waqar Younis, it's all about hard work in the nets. He chats with Wasim, he chats with Waqar, and he chats with Shoaib Akhtar as well. He improves day by day, and he knows the tricks, all the yorkers and slower balls. He knows the art."

There was also strong criticism from Ijaz Butt, the PCB chairman, over Vettori's comments. "I didn't expect it from a cricketer like Vettori," he told Cricinfo. "I have a lot of respect for him, but he made a statement which is uncalled for. [Gul] would never do a thing like this."

Geoff Lawson, the former Pakistan coach, was commentating on Saturday's match at The Oval and noted that several New Zealand pacemen achieved subtle reverse swing towards the end of their innings.

"My first reaction after reading [Vettori's] comments was of being pretty disappointed," Lawson told Cricinfo. "It sounded as if an issue was being made just because the New Zealand batsmen couldn't play him. There was no great mystery to what he was doing. He was bowling it nice and full and getting it to go just enough, not metres.

"I was commentating the game, and we were noting on air that some of the New Zealand bowlers were getting it to go a little bit reverse when they were bowling full towards the end of their innings. Gul was the best bowler at the last World Twenty20 and it's pretty disappointing for New Zealand to have made an unofficial approach. It seems Pakistan carry the cross for these kinds of things."

(With Alex Brown and Nagraj Gollapudi)

Andrew Miller is UK editor of Cricinfo