BP's decision to accept a record $4.5bn fine to resolve all criminal charges relating to the Deepwater Horizon blowout in 2010 has taken the total bill – money already paid out or set aside – to $42bn – and the costs could yet escalate further.

The oil group could still find itself open to more than $60bn worth of liabilities if it is found guilty of gross negligence in forthcoming court actions – although analysts suggested that outcome seems less likely after yesterday's agreement.

The new fine, the largest in US criminal history, is another blow to British business prestige, coming barely four months after the UK flagship drugs company, GlaxoSmithKline, was hit with a $3bn US fine, the largest in the pharmaceutical sector. British banks such as Barclays have also faced huge penalties from US regulators in recent months.

BP, once the biggest business on the London Stock Exchange, accepted that it had engaged in "negligent conduct". It pleaded guilty to 11 charges of manslaughter and "misdemeanours" under the Clean Water Act.

The London-based company said the resolution was "in the best interest of shareholders" but it still faces a raft of civil claims. It is also in the final stages of tying up a settlement with private claimants worth a further $7.8bn.

"All of us at BP deeply regret the tragic loss of life caused by the Deepwater Horizon accident as well as the impact of the spill on the Gulf coast region," said Bob Dudley, BP's chief executive. "From the outset, we stepped up by responding to the spill, paying legitimate claims and funding restoration efforts in the Gulf. We apologise for our role in the accident, and as today's resolution with the US government further reflects, we have accepted responsibility for our actions."

BP has accepted in this latest deal that it will be "on probation" for five years and has agreed for two "monitors" to check its activities for at least four years under a groundbreaking deal that settles all criminal and "securities" claims from Washington.

Peter Hutton, an oil analyst with RBC Capital Markets in London, said he was reassured the settlement was "positive" in the fact that it made no mention of "gross misconduct" – a charge that would trigger more heavy claims under the Clean Water Act.

Since the event in April, 2010, BP has been selling off billions of pounds' worth of assets all around the world to ensure it had a near-$40bn war chest to pay fines and other liabilities.

Among the businesses that it has looked to dispose of has been its 50% stake in its Russian joint venture, TNK-BP. The British company is currently finalising the sale of its holding to the largely state-owned group, Rosneft, along with a share swap.

Last month BP sold its troubled Texas City refinery – where 15 people died and 170 were injured in an explosion in 2005 – to Marathon Petroleum for $2.5bn.

The UK energy group also recently hived off its Carson refinery to Tesoro for $2.5bn and disposed of oil- and gasfields in the Gulf of Mexico to Plains Exploration for $5.5bn.

When the Macondo well blew out, it caused an explosion that killed 11 oil workers and triggered one of the worst environmental disasters in American history. Hundreds of miles of beaches were left covered in black tar, thousands of seabirds were killed and hundreds of fishermen lost their livelihoods.

"We believe this resolution is in the best interest of BP and its shareholders," said Carl-Henric Svanberg, BP's chairman. "It removes two significant legal risks and allows us to vigorously defend the company against the remaining civil claims."

As part of the resolution, BP has also agreed to plead guilty to one misdemeanor count under the Migratory Bird Treaty Act and one felony count of obstruction of Congress. This resolution is subject to US federal court approval.

Thirteen of the 14 criminal charges pertain to the accident itself and are based on the negligent misinterpretation of the negative pressure test conducted on board the Deepwater Horizon. BP acknowledged this misinterpretation more than two years ago when it released its internal investigation report.