Senior tax advisers have been put on the spot by law lords about what their respective codes of conduct at their accounting firms and within their professions suggested with regards to how they advised multinationals that operate in developing countries.
Pursuing the question of compliance with the law, Lord Shipley asked: 'You said that you will always comply with the law - but what happens when the law is known to you to be deficient?'
E&Y's global head of tax policy, Chris Sanger said that the firm will continue to still advise its clients.
'And separately we will give advice to governments and would help them to enhance their tax regimes. Be that through ATAF [African Tax Administration Forum] or individual governments to help ensure they have a sensible tax system,' said Sanger.
PwC tax partner Richard Collier however said the firm did not differentiate between regimes: 'We don't make a distinction between developing or non-developing countries - though they all apply the tax code. One of our requirements for the way in which we operate is that we will never work within a framework of not having full disclosure.'
On publishing of companies' tax information, Collier said that NGOs had raised concerns about this - and suggested it was therefore useful in the context of developing countries to publish information so that authorities need information to check that they're getting the right amount of tax due.
'It could be something which we share with the tax authorities in that country - the activities of the company in that country it will be more useful than large amounts of data that's submerged in the accounts,' said Collier.
Deloitte's group head of tax policy, Bill Dodwell, said that guidance for tax professionals was currently being updated, in addition to firms' individual practice manuals and guidance.
'If anybody felt we had failed to live up to our standards and if we don't deal with them satisfactorily, then thy go to whichever professional body they choose. Certainly complaints come into the firm and we will look to resolve that by whatever means is necessary,' said Dodwell.
When pressed on the number of complaints by Lord Clifton, he said: 'There are not masses of them, and one of the things the professional bodies are presently working with HMRC on is to encourage HMRC to raise complaints as well.'
The House of Lords' Economic Affairs Committee asked the questions of senior figures at Deloitte, Ernst & Young, PwC and Mercer & Hole as part of their inquiry into the issue of high profile companies criticised for the amount of tax paid in the UK.
Tax campaigners such as Christian Aid and the Tax Justice Network have repeatedly lobbied for attention on the issue, claiming that multinational companies use complex tax rules to avoid paying the full amounts of tax that they ought to.
The hearings - which will also include evidence from senior legal representatives who advise multinational companies as well as a representative of the Organisation for Economic Development and Cooperation (OECD), which is currently engaged with reforming the international tax framework - are expected to continue until mid-June.
