Christianity Uncut, a UK-based economic justice group is encouraging Britons not to do business with companies such as Amazon and Starbucks during Lent as a public witness against their sins of corporate tax avoidance.

As Lent began with Ash Wednesday the Rev. Chris Howson, a Church of England priest in the north eastern England city of Sunderland anointed his local branch of Starbuck's with ashes, traditionally used as a call to repentance.

The issue of corporate tax avoidance has been hotly debated in recent weeks, but Amazon and Starbucks have defended their records saying they are obeying the law, create jobs in area where employment is needed and that investments have kept their profits low.

Angel Gurría, head of the Paris-based Organization for Economic Cooperation and Development warned on Tuesday that governments need to modernize their tax systems to catch international companies that avoid paying corporation tax.

"As governments and their citizens are struggling to make ends meet, it is critical that all tax payers - private and corporate - pay their fair amount of taxes and trust the international tax system is transparent," said Gurría.

A Member of Parliament for Britain's ruling Conservative Party, Stephen McPartland, caused a stir when he wrote a recent article in the Communist Morning Star newspaper calling for greater tax transparency for large corporations. It was the first time the newspaper had featured an article from a Conservative lawmaker.

"Tax justice campaigners believe that tax-dodging by international companies costs Britain around 35 billion pounds and developing countries an estimated 100 billion pounds ($157 billion) a year", he wrote."Just imagine the dramatic difference such a huge sum of money would make if it were available to invest in public services".

Christianity Uncut, a network of anti-capitalist Christians, suggested that a crackdown on tax avoidance is a better way of reducing the national deficit than cutting public services and Britain's welfare state.

"Tax justice is a pressing issue. Amazon, with its aggressive tax avoidance policy, can easily out-compete British-based high street firms. For lent, there will be no more cheap books for me from this tax dodger," said Howson.

"As for Starbuck's, not only has it evaded millions of pounds of corporation tax over the last few years, it has tried to publicly bribe the government, instead of simply paying its tax!"

The group says individual Christians will reach different conclusions about which companies to target and whether to continue with the boycott beyond Lent.

But it suggested that lots of Christians working acting on the issue in their personal spending could be both an important witness and a form of economic pressure.

Other ideas for the 'tax justice fast' include moving money from banks that have avoided tax, such as banking giant Barclay's, and committing to shopping locally.

"Join me, and let's support those who pay their taxes so that our kids get a decent education, bins are collected, and people can be looked after by the NHS (National Health Service)," Howson was quoted saying by Christianity Uncut.

"Make up your own version of the Tax Justice Fast for Lent," he said.