CRANE operators working on the new Queensferry Crossing have walked out in a strike over pay.

The consortium in charge of the flagship project said they had put in place resources to "minimise any potential disruption" after employees of mobile crane hire firm, Ainscough, downed tools.

The strike was the first in a series of escalating actions planned over the coming weeks through to March 23.

Nine of the cranes used on the Queensferry Crossing site - also known at the Forth Replacement Crossing - are operated by Ainscough.

The project, which will replace the Forth Road Bridge as the main traffic link between Fife and the Lothians, is expected to be completed by the end of this year.

However, a spokesman for the Forth Crossing Bridge Constructors (FCBC) consortium said the main works were still continuing to plan.

He said: “There are currently nine Ainscough operated crawler and mobile cranes, working on land or barges on the Forth Replacement Crossing construction site. The three principal tower cranes and the cranes involved in the current deck segment lifting operations are not Ainscough cranes and their operation is not affected by this strike.

“FCBC has put in place the necessary flexibility and resources to minimise any potential disruption.”

A spokeswoman for Amey, the maintenance firm in charge of repairs to the Forth Road Bridge, said it would not be affected by the ongoing industrial action as none of the cranes used at the FRB belonged to Ainscough.

Members of the Unite trade union, which represents 500 crane operators and support staff members across the UK, voted 90 per cent in favour of a strike in protest at what Unite dubbed a "pitiful pay offer".

Ainscough has offered a two-year pay hike split between a 2.5 per cent pay increase in the first year and another 2.75 per cent increase in the second year.

Unite members plan a further 24-hour walkout on February 8, followed by a series of two and three-day strikes beginning on February 15 along with various overtime bans.

As well as the dispute over pay, Unite has also raised fears about plans to introduce zero hours contracts in "safety critical industry".

Unite national officer for construction Bernard McAulay, said: “However we fear that the drive to lower pay for the workforce won’t stop with this pay offer. We are extremely concerned that Ainscough is now drawing up plans to rip up the industry-wide agreement by introducing zero hours contracts for a pool of workers.

“These workers will then be on hire and fire contracts reducing them to a disposable workforce. This will have serious safety implications for what is already one of the most dangerous industries in the country."

Ainscough denies it has any plans to introduce zero-hours contracts, and accused Unite of misrepresenting the offer on the table.

A spokesman said the pay offer also included performance bonuses, enhanced mileage rate and improved annual leave arrangements.