Britain's offshore rigs and platforms have leaked oil or other chemicals into the North Sea on 55 occasions over the past month alone, challenging claims by the industry that it has a strong safety and environmental record.

Among the fields to have reported pollution discharges is Piper Alpha, the scene of the world's worst offshore accident in terms of fatalities when it blew up, killing 167 workers, 25 years ago.

Facilities operated by Shell, BP and BG were all offenders, according to the latest petroleum operations notices (PON1s) reported to the Department of Energy and Climate Change (DECC).

Greenpeace said the alarming statistics should act as a reality check for an industry that was trying to persuade the world it should be allowed to drill in the pristine waters of the Arctic.

"They're trying to convince the world that they can operate safely in one of the world's harshest environments, yet they can't prevent this steady trickle of oil and other polluting chemicals leaking into the relatively safe waters of the North Sea," said Greenpeace senior climate adviser Charlie Kronick. "This will do little to increase public trust in their ability to drill in the Arctic without damaging this incredibly beautiful and fragile corner of our planet."

But the industry itself says the leaks often contain tiny amounts of relatively harmless substances and the reporting system is an example of a good regulation.

One of the worst offenders in the latest set of DECC figures is Shell, which on 3 June reported lubricant and other chemical discharges from its Brent Bravo and Brent Charlie platforms.

A Shell spokesman said: "Asset integrity and process safety is Shell's foremost priority at all times. No spill is acceptable and we work hard both offshore and onshore to minimise risks to maintain a safe working environment for our workforce and reduce any environmental impact on the North Sea.

"Shell is actively participating in the Step Change in Industry safety initiative, which includes a focus on hydrocarbon spill reduction. The industry has achieved an almost 50% reduction in hydrocarbons leaks during 2012, based on a baseline set in 2009."

In 2006, Shell was fined £900,000 after pleading guilty to safety lapses on the Brent B platform following an accident in 2003, when the facility was hit by a gas leak in which two oil workers died.

BP, which is still fighting criminal charges following the Deepwater Horizon accident of 2010 in the US Gulf, is reported to have had crude leaks off the Paul B Loyd Jnr rig, which was working on the Clair field on 6 June this year. There was also a release of "another" substance from the same drilling unit two days earlier. On 25 May there was discharge on the Marnock field.

BG had a leak on the Everest North platform on 31 May while Talisman Energy discharged chemicals the day before on the Piper Bravo platform – which replaced Piper Alpha (destroyed by fire in 1988.)

Petroleum operations notices are all reviewed and investigated by an offshore environmental inspector as they are reports of potential breaches of DECC-enforced regulations.

Some of the discharges are allowable under North Sea rules but most on the latest PON1s monthly data whose status is marked "completed" rather than still "under review" ascribed the source to various mechanical failures.Those incidents that do show how much product was released indicate small amounts but any unintended action is unwelcome at a time when safety and the environment are major concerns of the public.

Although the PONS1 data seen by the Guardian for the month from 6 May to 6 June show 55 different numbered notices, employers dispute the figures and downplay their significance.

Mick Borwell, Oil & Gas UK's environmental issues director, said: "The vast majority of the 103 spills this year [in PON1 reports] are very small operational chemical spills. They have no potential to cause a major accident."On Monday, BP will appear in court in New Orleans to argue that the huge compensation package agreed last year following the Deepwater Horizon disaster is being abused. Lawyers for BP will claim that large numbers of "fraudulent, excessive or improper claims" are being filed to the victims' fund, to which BP set aside around $8bn.