The Public Expenditure Minister Brendan Howlin says there is 'no fear' at all of any religious being prevented from espousing their views on same-sex marriage.

Mr Howlin was commenting after religious orders, including Muslim and Quaker groups, called for a 'conscience clause' to be including in the referendum next month.

It would allow people to ignore gay marriage rights in certain circumstances.

Mr Howlin says the only issue at hand is whether all citizens 'regardless of sexual orientation' should be treated equally under the Constitution.

He says the conscience issue is a 'red herring'.

Last month, the Tánaiste also ruled out a so-called 'conscience clause' for opponents of the measure.

Joan Burton said she cannot see any circumstances were businesses would still be allowed to discriminate on the basis of their own beliefs.

She was responding to calls from Dublin Archbishop Diarmaid Martin, who wants businesses to be able to turn down business from same-sex couples - even if the referendum is approved in two months time.

He sees it as a way for businesses to opt out of providing goods or services for gay weddings if the referendum is passed.