David Cameron and George Osborne made a "massive mistake" in courting China from 2010 to 2016, Sir Iain Duncan Smith has told Sky News.
The former Tory leader said the Yang Tengbo spying row proves that aspects of national security were overlooked and the UK is now paying the price.
Sir Iain, who served in Lord Cameron's cabinet from 2010 until 2016, spoke to Sky News after his urgent question in the Commons on China and spying allegations.
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Asked if Lord Cameron and Mr Osborne's courting of China was to blame for some of the problems of national security the UK is facing now, he said: "It was a massive mistake.
"I made that pretty clear at the time. I was in government at the time, I was very uneasy about what they were doing. I didn't think this would work. It turns out that it didn't work.
"I thought it was a big mistake because President Xi is smart enough to know that we're coming to court him. Well, we have to pay a price for that. And the price we pay is to overlook aspects of national security."
Sir Iain also said he believes Sir Keir Starmer's government is now bowing to pressure from MPs to bring in a foreign influence registration scheme (FIRS), initially proposed by the Conservatives before the election.
"It wasn't so long ago when the prime minister refused to answer a question, only about two or three months ago, as to whether or not they would do anything with it," Sir Iain said.
"Now at least he's moved, being pushed by us, I think, to actually do something about it. The one outstanding question is will China go into the upper tier of the registration scheme, which would make them the single biggest threat?"
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Referring to security minister Dan Jarvis, who answered his urgent question, Sir Iain said: "I think the minister wants to do it. I don't question his desire to do it, nor the security forces who will want to do it.
"What I question is that businesses and banks and some government departments, as I understand it, were all pressurising the security apparatus not to introduce FIRS because they were worried it would upset the Chinese.
"Only now, after this spying case and our pressure over that on all sides, I think the government's now stepping in again to redo it. It looks like it will come in even if it's late."
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