United Nations, Mar 19 (IANS): The UK's decision to increase its nuclear arsenal is inconsistent with the Nuclear Non-Proliferation Treaty (NPT), a UN spokesman said.

The position marks a toughening from earlier in the week, when Stephane Dujarric, the chief spokesman for UN Secretary-General Antonio Guterres, expressed concerns over the UK's announcement, Xinhua news agency reported.

"While the UK continues to support the goal of a world free of nuclear weapons and many efforts to achieve it, the UN feels this announcement is not consistent with the disarmament commitments all nuclear-weapon states have undertaken," Dujarric said on Thursday.

The announcement also is inconsistent with commitments under the consensus outcome from the 2010 NPT Review Conference, he said.

That accord seeks to "undertake further efforts to reduce and ultimately eliminate all types of nuclear weapons" and "rapidly move towards an overall reduction in the global stockpile of all types of nuclear weapons".

On Tuesday, the spokesman said the UN was studying the UK report.

The next day, he expressed the world body's concern, saying the UK decision was contrary to the country's obligations under Article VI of the NPT.

"It could have a damaging impact on global stability and efforts to pursue a world free of nuclear weapons.

"At a time when nuclear weapon risks are higher than they have been since the Cold War, investments in disarmament and arms control is the best way to strengthen the stability and reduce nuclear danger," he said on Wednesday.

The UK government on Tuesday announced its plan to increase the number of nuclear warheads to not more than 260, reversing its previous policy of reducing its overall nuclear warhead stockpile ceiling to not more than 180 warheads by the mid-2020s.

Outlining the strategy to MPs, Prime Minister Boris Johnson said the UK would have to "re-learn the art" of competing against countries with "opposing values".

But he added the UK would remain "unswervingly committed" to the NATO defence alliance and preserving peace and security in Europe.