Sinn Féin deputy leader Mary Lou McDonald has been challenged on the party’s tax proposals while canvassing in Dublin.

Ms McDonald was unveiling the party’s latest billboard ahead of the water charge rally on Saturday on Grafton Street in Dublin.

A small business owner, who declined to reveal his name but insisted he was non-political, strongly criticised the party’s measures on tax.

The man said Sinn Féin “would strip the middle income earners” and described their proposals as appalling.

He also questioned whether party leader Gerry Adams understood basic maths.

The business owner conceded he would be voting Fine Gael due to their proposals on Universal Social Charge.

The small business owner said: “What about people who work hard and try and make a life for themselves? You want to punish them.”

In response Ms McDonald said she understood it was not universally popular to introduce a third rate of tax.

However, she said it was required if the books were to be balanced and services was to be protected.

The Sinn Féin deputy leader said people with the deepest pockets needed to pay the most.

Ms McDonald also defended her party leader who has been criticised for his weak recent performances on broadcast media when discussing the economy.

She said she had not heard the interviews on RTÉ’s Sean O’Rourke programme and Six One news yesterday.

However she said: “Anybody can fumble a figure in an interview.”