The move to the new parliament building is expected to be made in 2020, he said.

The delay – the third time since the contract was signed in 2013 – has been caused by complications in the construction of the underground compound which requires excavation of two million cubic metres of soil, said project director Pheera Nakwimol.

There were two other complications, he said. One was the half-sphere auditorium which perches on metal structures without columns, Pheera said. These structures weigh 2,500 tonnes and must be assembled at the site because no logistic means are available, he said.

Another was the traditional Thai-styled finials. The engineer said the design would take three months longer than had been planned.

Kicking off in June 2013, the Bt12-billion contract won by Sino-Thai Engineering and Construction PLC, was expected to be complete in November 2015. However, it was postponed to November 2016 and to February 2018 before the latest deferral announced yesterday. As of August 2017, the construction has progressed to 38 per cent.