For more than 150 years, Big Ben has rung out reassuringly during times of war and peace.

Not even Nazi bombs could silence the famous symbol of Britishness. But having marked the hour with almost unbroken service since 1859, the Great Bell's bongs will soon cease for four years – because of health and safety.

Big Ben is to be silenced amid fears workers involved in a restoration project could have their hearing damaged. Authorities say it would be 'unacceptable' to expose workers on scaffolding surrounding the bell tower to the noise of its chimes – and also 'unacceptable' for them to wear ear defenders.

They say they owe the workers 'a duty of care' on health and safety grounds, but the decision triggered an outcry last night.

Authorities say it would be 'unacceptable' to expose workers on scaffolding surrounding the bell tower to the noise of its chimes (pictured)

The Great Clock was last stopped for maintenance in 2007, when workmen abseiled down the face to carry out cleaning

Currently, workmen are on the scaffolding which surrounds the famous tower for up to eight hours a day

Labour MP Steve Pound said: 'They kept the bells tolling through the Blitz. The Luftwaffe could not stop it but health and safety has. There has to be a way around this.'

The bell at the north-eastern end of the Houses of Parliament in Westminster will ring for the last time at noon next Monday. The renovation of the Elizabeth Tower is expected to be completed by 2021.

A spokesman for the Parliamentary authorities said: 'The chimes are being stopped to provide a safe environment for the people working on the scaffolding. Constant proximity to the chimes would pose a serious risk to their hearing, and prevent efficient working.'

Officials stressed that Big Ben would still chime during the renovation – by special arrangement – to herald the New Year and on Remembrance Sunday. But shadow international trade secretary Barry Gardiner asked why it could not chime at noon each day – the time when hundreds of tourists gather in front of it.

'It does rather beg the question why it's going to take four years to do this,' Mr Gardiner said. 'Big Ben has resonance and importance for the tourist industry. This should have been taken into account.

'It also seems to me not beyond the wit of man to make sure the programme of works could be arranged in a way that would allow it to chime more regularly. It seems to me draconian to think it will only chime eight times in four years.'

Tory MP Shailesh Vara said: 'Why should it be taking four years? Are they working three shifts in 24 hours, or are they doing a 9 to 5?'

Steve Jaggs, 53, who holds the title of Keeper of the Great Clock and leads a team of three mechanics who visit the tower three times a week to wind and oil it, told the Mail the reason for silencing the bongs was 'health and safety and duty of care'.

He added: 'The workmen on the scaffolding are working eight hours a day with the noise of the bells which is unacceptable. It would also be unacceptable for them to be asked to wear ear defenders for that length of time.' Asked why the work would take four years, Mr Jaggs said: 'You have to get everything right. There's a lot of unknowns. It's very complex conservation work.'

Big Ben will fall silent for far longer than was envisaged when the project was announced in April last year

The 315ft Elizabeth Tower, which was completed in 1856, needs work to repair cracks in the masonry, corrosion to the cast-iron roof and belfry and the frame which holds the bells - including Big Ben

The tower's cracked masonry needs repairing and work needs to be done to prevent condensation which has led to rust in the belfry. The clock's mechanical mechanism has never been properly serviced and will be taken apart for the first time, he said.

The Great Clock will be dismantled piece by piece with each cog examined and restored. The four dials will be re-glazed, the cast-iron framework repaired and the hands will be removed and refurbished.

A spokesman for the parliamentary authorities said: 'The Elizabeth Tower, home to the Great Clock and Big Ben, is currently undergoing a complex programme of conservation works necessary to safeguard it for future generations.

'While vital restoration work takes place, the Great Bell's world-famous striking and chiming will be paused until 2021 to ensure the safety of those working in the Tower.'

Asked why the bells could not be rung more often, the spokesman said: 'Our team of clock mechanics have a well-practised method of stopping the bells. The striking hammer will be locked and the bells disconnected from the clock mechanism. The weights will then be lowered within the weight shaft to the base of the tower and secured. The whole process is expected to take approximately half a day to complete.

'The process to reconnect the bells is lengthy and it would not be practical or a good use of public money to start and stop the bells each day.'

One working clock face will be visible throughout the works, the hands of which will be driven by an electric motor, the spokesman added.

Concerns were also rising last night that the cost of the renovations could spiral past the original £29 million estimate, with some sources claiming the cost has doubled to £60 million. The money is coming from the Medium Term Investment Plan of the Parliamentary Estates.

The BBC, which uses the live sound of the chimes to introduce the 6pm and midnight news on Radio 4, will use a recording instead.

Formerly known as the Clock Tower, the 315ft structure was renamed the Elizabeth Tower in 2012, in honour of the Queen's Diamond Jubilee. Big Ben strikes on the hour in the note of E. There are four smaller bells beneath it that ring on the 'quarter' hours. They strike the notes G sharp, F sharp, E and B.