LONDON (Reuters) - Britain's biggest telecoms service providers have filed a complaint to media regulator Ofcom demanding greater competition in the business broadband market, where they say BT (>> Banque de Tunisie SA) has an effective monopoly.

The UK Competitive Telecommunications Association (UKCTA), said other companies should be allowed to lay their own cables in BT ducts and use their own equipment to control BT cables, saying it would improve service and encourage innovation.

The group, which includes firms such as Sky (>> British Sky Broadcasting Group plc) , EE (>> ORANGE SA) (>> Deutsche Telekom AG), TalkTalk (>> Talktalk Telecom Group PLC) , Virgin Media (>> Liberty Global PLC) and Vodafone (>> Vodafone Group plc), also said many consumers did not know who was responsible for the network when services were disrupted.

BT's network business Openreach, which manages the national telecoms network, continues to dominate the business end of the market, 30 years after the company was privatised.

A BT spokesman said in a statement that forcing Openreach to open up access to BT ducts would increase costs and that the company was voluntarily publishing its service performance to reflect its commitment to improving service.

"The UK has a vibrant wholesale business connectivity market, with strong competition and innovation amongst a large number of providers," he said.

Ofcom said its work “goes hand-in-hand with promoting competition".

"The UK already has the most competitive broadband market of any major European country," a spokesperson said.

"Our job is to ensure that customers benefit not only from innovation, but also from good quality of service and a fair deal.”

(Reporting by Li-mei Hoang; Editing by Jon Boyle)