Billionaire football club owner Roman Abramovich fears a police radio mast built under the cloak of darkness near his luxury estate is a health risk.

The Russian tycoon and Chelsea boss is worried the Tetra mast, which does not have planning permission, will make his staff sick.

O2 Airwave, whose parent company O2 UK sponsors rival club Arsenal, was refused planning permission for the development but went ahead regardless, provoking outrage from home-owners nearby.

Mr Abramovich, who earned £564 million last year, owns a 424-acre estate worth £12 million at Fyning Hill, near the development site at Forge Farm, Rogate, near Midhurst.

Estate manager Dean Hall wrote to council leaders on behalf of his boss when the mast was first proposed.

Mr Hall said: "Mr Abramovich is concerned for the health of his employees. Our concerns are that the Government is implementing this Tetra system without it being fully tested with regards to the way it affects people's health.

"O2 erected that mast without the necessary planning consent and they feel they can run roughshod over us but this is a Government scheme and it seems to me different rules apply to them."

Campaigners yesterday held a vigil at the site to stop engineers switching the mast on.

Norman Coleshill, 63, a retired finance worker for IBM, said: "The local population, particularly those with kids, feel there is a risk of cancer.

"The parish council is livid because this mast has been turned down for planning permission and has been put up with total disregard for all democratic processes."

John O'Brien, who heads the Protect Sussex from Tetra protest group, said there were two main health concerns.

He said: "Firstly, Tetra is a system that uses electro-magnetic radiation in the microwave range. There is a lot of evidence to suggest it is cancerous in the long-term.

"Secondly, Tetra emits a pulse at the same frequency as used by the brain.

"This constant overwhelming electronic force overwhelms the body's ability to communicate and distorts the body's own mechanisms."

There have been reports of people living near masts suffering headaches, sickness, migraines, disturbed sleep and skin rashes.

A protest was also held at Bowhill Farm in East Marsden, near Chichester, where another mast was put up over the weekend, again without permission.

Planning officers at Chichester District Council say the masts had not been given planning permission and ordered the phone company to remove them by 1pm on Wednesday or face an injunction.

Sam Howes, deputy chief executive of Chichester District Council, said: "We want to assure the public we are taking this very seriously and will inform them of the action taken."

An O2 Airwave spokesman admitted the masts had been put up before planning permission had been granted to meet the firm's deadlines.

He said: "Delays in the planning process have required O2 Airwave to build ahead of receiving full planning approval.

"While we regret the need to proceed in this way, this is an exceptional measure that has not been taken lightly and any site that is to become a permanent part of the Airwave network must achieve approval."

He also admitted the firm deliberately sneaked the mast in during the small hours.

He said: "We are well aware of the fact there is a lot of opposition and it wouldn't do anyone any favours to build at a time when there could have been quite a lot of activity in terms of protests."

About 87 Tetra masts are essential to bring Sussex Police's new £2 million radio system on line.

Airwave O2 said about three-quarters had been erected so far.

Police hope to start using the system in Brighton and Hove in March.