Microsoft executives telephoned Conservative MPs threatening to shut down a facility in their local area because of planned IT reforms, David Cameron’s former strategy chief has claimed.

Steve Hilton, who worked for Cameron in opposition and for two years in Downing Street, made the allegation as he argued the dominance of corporate lobbying in the UK was leading to bad policy-making.

Asked how the government should deal with lobbyists, he said: “You just have to fight them off. I can give you specific examples: the thing I mentioned about IT contracts. Maybe there is someone here to confirm this from Microsoft? When we proposed this, Microsoft phoned Conservative MPs with Microsoft R&D facilities in their constituencies and said, ‘we will close them down in your constituency if this goes through’.

“And we had the same from other tech companies as well … We had the stories from the MPs saying I’ve just had this call from – sometimes a global CEO – phoning a Conservative MP, saying we will close down this plant. We just resisted. You have to be brave. You just have to say sorry: it’s the right thing to do.”

Steve Hilton, the former Conservative party strategy chief, said government had to ‘fight off’ lobbyists. Photograph: Sarah Lee/The Guardian

However, Hilton also appeared to concede that lobbying sometimes works. Speaking in Westminster to promote his new book, he said he felt very strongly that lobbying often led to “terrible outcomes, such as a devastating impact on our health and environment” caused by the vested interests of big food companies successfully defending “toxic junk that ends up being fed to our children”.

He was severely critical of the lobbying industry despite being married to a senior public affairs executive, Rachel Whetstone, who has worked for Google and is now at Uber.

Another former Downing Street aide, Rohan Silva, appears to have given a similar account of lobbying by Microsoft in relation to open source software, in comments reported by Computer Weekly.

Silva told a conference: “A day or two before we were going to give a speech, a couple of backbench MPs called the office – they said Microsoft had called them saying if we went ahead with the speech on open standards, open architecture and open source, they would cut spending or maybe close research and development centres in the constituencies of the MPs they had called.

“I was pretty worried about this, to be honest. I went to see George [Osborne] and he said if Microsoft have a problem with the speech they should call us directly. I relayed that back to the MPs and we never got a call from Microsoft, so we went ahead with the speech. But for the public affairs department, the relationship was never quite the same.”

Microsoft for years opposed the Conservatives’ position on open document standards, which was advocated from 2007 but not adopted by the government until 2014. The government’s standard is now open document format (ODF), which means files can be opened with free software, rather than commercial products.

A Microsoft spokesperson said: “We have looked into the nearly decade-old matter and we don’t recognise these claims. Fundamentally, it is not how we operate as a business. We have an honest and open engagement with the government and this is how we will continue to work with it.”