• PM's office unveils two inquiries into child sex abuse claim • North Wales inquiry and police response to be reviewed • As many as five child abuse inquiries 'imminent' • Tom Watson praises PM but calls for wider investigation

The government is racing to stay ahead of the swirl of allegations about child abuse in the UK by announcing two further inquiries into an alleged abuse ring in north Wales in the 1970s and 1980s.

The first inquiry will look into the conduct of the original official inquiry into the child sex abuse ring and the second into the police handling of complaints at the time.

Faced by allegations that senior Conservative politicians may have been involved in the scandal at the time, David Cameron, while on an official visit to the Middle East, announced he would establish an urgent investigation into the conduct of the official inquiry held between 1996 and 2000.

In addition, the prime minister's spokesman in London said a separate inquiry will be held into the way in which the police handled the investigation.

The spokesman conceded as many as five different inquiries were now underway, or imminent, looking into aspects of child abuse.

The spokesman did not rule out an over-arching figure being asked to look at the lessons to be drawn from the inquiries now covering the BBC, the NHS, the police and government.

Cameron rushed to act as the media threatened to identify the senior Tory figure close to Lady Thatcher alleged to have been involved in the child abuse.

The Labour MP Tom Watson also urged the government to act after victim Steve Messham said that the Waterhouse inquiry of 2000 only covered a fraction of the alleged assaults.

Speaking in Abu Dhabi, Cameron said: "Child abuse is an absolutely hateful and abhorrent crime … These allegations are truly dreadful and they mustn't be left hanging in the air, so I'm taking action today.

"I'm going to be asking a senior independent figure to lead an urgent investigation into whether the original inquiry was properly constituted and properly did its job and to report urgently to the government."

Cameron also called on anyone who knows anything about the allegations of abuse to contact police.

Cameron said Messham would meet with the Welsh secretary, David Jones, on Tuesday.

Cameron cannot afford to be seen to be delaying any action concerning the allegations due to their seriousness, but also because the government has been so criticial of the BBC's own failure to act on allegations about child abuse by Jimmy Savile.

In an extraordinary letter to the prime minister, Tom Watson praised Cameron for acting swiftly, saying: "You have sent an important message about how seriously you take this matter."

However, he also made a series of further allegations. "It is certainly important that government departments trawl their archives to see what documents they hold," said Watson. "But my experience of uncovering massive establishment conspiracies leaves me in no doubt that what you have suggested does not go anything like far enough. Its limited scope may even slow things down, muddy waters, damage trails. What is needed is a much wider, but equally immediate, investigation."

He adds: "Since sharing my concerns with you at PMQs, a number of people have come forward to say that they raised their suspicions with the police, but investigations were not carried out. One allegation involves alleged child abuse and a former cabinet minister. We both know that many untruths are told about politicians, but this allegation was specific, informed and appeared well corroborated."

The prime minister's official spokesman insisted Cameron was "very keen to ensure that everything is looked at properly and thoroughly and that no stone is left unturned".

The BBC's Newsnight programme on Friday night accused a senior Tory of abusing children at a care home in north Wales. According to reports at the weekend, as many as three victims have named the Tory grandee as one of their abusers.