Shanghai's mayor promised Sunday to speed up development of China's first free trade zone (FTZ) a year after it opened, as a chorus of foreign companies expressed disappointment over the pace of pledged reforms.

The FTZ was set up in China's commercial hub Shanghai last September with the promise of a range of financial reforms, including full convertibility of the yuan currency and free interest rates -- which remain unfulfilled.

Mayor Yang Xiong said the government would work towards making the yuan -- also known as the renminbi (RMB) -- freely convertible, among other financial liberalisation plans for the FTZ, but gave no timetable.

"We will gradually put in place an institutional and regulatory framework to enable the convertibility of the RMB under the capital account... so that the financial sector can better serve the real economy," he told business leaders in a speech.

China keeps a tight grip on its currency fearing unpredictable inflows or outflows of funds could harm the economy and reduce its control over it.

Yang said the government would also offer a revised "negative list" of what is barred in the FTZ for 2015, following criticism that the two previous lists were too long.

"We will further liberalise the service sector by rolling out a series of new measures and compiling the 2015 version of the negative list," he said.

Foreign business executives attending the annual meeting, which bills itself as an advisory body to the city government, said they were waiting for clarity.

"The resulting time lag between announced and actually implemented reform measures has created an opaque picture that has led to a wait-and-see attitude among many foreign investors," Michael Diekmann, chairman of German insurance giant Allianz, said in a paper presented at the meeting.

Some 12,600 companies had registered in the FTZ since its establishment but only 14 percent were foreign-invested firms, according to official figures.

"A lot of financial reforms in favour of liberalisation have been announced but have not yet been implemented or not completely, such as the liberalisation of RMB," Gerard Mestrallet, chairman and chief executive officer of French energy firm GDF Suez, said in another paper.