A former Google employee turned whistleblower, whose evidence is crucial to a parliamentary report released on Thursday into the search engine's tax affairs, has explained that his decision to speak out was rooted in his Christian beliefs.

Barney Jones, a father of four, said he felt compelled by his faith to give evidence to the public accounts committee. He was prompted to do so after reading what appeared to be misleading evidence from a senior Google executive claiming that the company did not sell products in the UK and therefore owed no tax there.

Jones, 34, a member of the sales team for the company between 2002 and 2006, said he could think of no material benefits to speaking out, but he would do it again if a company he worked for was involved in an "immoral" tax scheme.

"I don't think there has been any real benefit to me for standing up. The main benefit is knowing that, as one day we will all be held accountable for our actions – I believe that Jesus will hold us accountable for the good and bad we have done – I will know that I didn't allow something within my power to just slip through. But I stood up and said: 'Well, actually this is a wrong thing, and this is something we have to think about,'" he said.

On the eve of the release of the committee's report into Google, which is expected to be highly critical, Jones said his career options had probably been damaged because prospective employers may see him as a troublemaker. But he expressed no regrets for explaining how the company sold products from London, but claimed that it only did so from Ireland, where corporation tax is much lower.

"If no one had stood up and said: 'I don't think this is the right thing,' we would not be having this particular debate about international taxation and therefore the British taxpayer would not get all of the money needed to build the next generation of hospitals and schools," he said.

Jones approached the public accounts committee in May after reading a newspaper account of the evidence from Matt Brittin, Google's vice-president, who told MPs: "Nobody [in the UK] is selling."

The dispute over tax revolves around Google's use of its European headquarters in Dublin to minimise its tax bill in Britain. By booking all UK sales through Ireland, it handed HMRC only about £10m in corporation tax over the period 2006-11. It is able to record the revenues in Ireland because the UK company is deemed to drum up new business, with sales staff in Dublin executing all deals.

But Jones said he attended meetings where Google's London sales staff closed deals. "I looked at his [Brittin's] story and could not believe what I saw," he said.

Jones left the company seven years ago but, like many Google employees, had copied his documents on to a memory stick because he had personal emails and photos among his work files. He has contracts, invoices and correspondence between Google and its customers in Britain, which have been seen by the Guardian.

Jones, whose father was a headteacher and whose mother was a social worker, gave his evidence to the committee.

Hodge recalled Brittin to give evidence to the committee, and concluded that the company's behaviour was "devious, calculated and, in my view, unethical".

Jones has spoken to former colleagues, some of whom still work at Google, and has received a mixed response from them, he said.

"Many have pointed out to me that by taking a stand on this I haven't made myself massively popular. My employment prospects for the future have been affected. Certainly a lot of companies that have a European HQ in Dublin are unlikely to be top of my list of future potential employers. But that's OK," he said.

Despite this, Jones, who lives in south London with his wife and children, said he would encourage others to blow the whistle.

Jones said he still thought of his time at Google with great fondness and hoped the company would return to its core values.

"Google is a great company and it has a great history and heritage of the management being held accountable to staff.

"I remember some wonderful town-hall-type meetings where Google staff got up and questioned senior management about what the company has done, the direction of the company," he said.

He said he hoped Eric Schmidt, Google's executive chairman, would listen to the committee's report. "I think Eric is bound to listen. I'm an ex-employee and quite a low-level one at that – but I know there are lots of other employees who are very concerned about the company doing the right thing by other countries and I am sure Eric will think long and hard about how to address this problem," he said.