The continued progress of the Transatlantic Trade and Investment Partnership (TTIP) has been called into question following criticism of the trade deal by ministers in leading European nations.

Negotiations over the broad-ranging trade alliance between the US and EU have been ongoing since July 2013, with the 12th round of talks coming to a positive conclusion earlier this year and strengthening confidence that the deal will be concluded before the end of the year.

However, the prospects of this happening have taken a hit in the last few weeks after German agriculture minister Christian Schmidt accused the US of not doing enough to make the conditions of the agreement favourable to German businesses.

Mr Schmidt told Der Spiegel: "So far at least, they have hardly made any serious concessions."

He said the incentives on offer in the automotive sector are not currently sufficient to garner support, while ruling out the idea of trading concessions in one industry for more favourable terms in another.

This comes after French president Francois Hollande also recently said that France would be likely to vote against TTIP in its current form, due to concerns that it would weaken regulatory oversight of the international trade sector.

He said: "We will never accept questioning essential principles for our agriculture, our culture and for the reciprocity of access to public [procurement] markets."

Despite these concerns, TTIP continues to have the backing of the leaders of many of the leading nations involved in the negotiations, with US president Barack Obama, German chancellor Angela Merkel and British prime minister David Cameron all vocal in their views that TTIP would have a positive impact on transatlantic trade and economic prosperity.