FP McCann Ltd - which has a major site in Littleport - is facing a fine of more than £25 million for breaking competition law by taking part in an illegal cartel covering Great Britain.

Two other companies are due to pay more than £7 million and £4 million respectively.

The fines were imposed after the Competition and Markets Authority (CMA) found that from July 2006 to March 2013, the firms agreed to fix or coordinate their prices, shared the market by allocating customers and regularly exchanged competitively sensitive information.

These arrangements continued for nearly seven years and involved meetings attended by senior executives from each of the firms. The CMA recorded a number of these meetings and used them as evidence when arriving at its final decision.

Pre-cast concrete products, such as drainage pipes, are of crucial importance to large infrastructure projects and are often used in roads and railways or water management projects.

Customers include engineering and construction firms, utilities providers and local and national government across Great Britain.

Andrea Coscelli, the CMA's chief executive, said: "These companies entered into illegal arrangements where they secretly shared out the market for important building products and agreed to keep prices artificially high. This is totally unacceptable as it cheats customers out of getting a good deal.

"The CMA will not hesitate to issue appropriately large fines in these cases and we will continue to crack down on cartels in the construction sector and in other industries."

FP McCann has been locked in a three year planning battle with East Cambridgeshire District over proposals for a £2 million extension that would double the size of the Littleport factory and create up to 90 new jobs.

Officials at East Cambs Council have recently told FP McCann there remain "too many issues yet to be resolved" and no decision can yet be given.

Local protest group Save our Fens believe the court £25 million fine has helped their case.

"We will fight to the end and we need the help of everybody in this area who has a sense of decency and a concern for our environment," said a spokesman.

FP McCann has called for a "firm, written assurance" that the application would be considered by the next available meeting of the planning committee.