Russia’s invasion of Ukraine has made members of the UK House of Lords tens of thousands of pounds richer through their investments in arms firms, openDemocracy has found.

Tory peers Lord Glendonbrook, Viscount Eccles and Lord Sassoon, and unaffiliated peers Lord Lupton and Lord Gadhia, each own shares of at least £50,000 in British weapons manufacturer BAE Systems, according to the official register of interests.

BAE Systems’ share price has risen by 23% since the war began nearly four weeks ago, meaning each peer’s investment is likely to be worth at least £11,500 more than it was.

The firm is Britain’s biggest arms seller and sixth in the world overall. All but four of the world’s 20 biggest sellers of weapons have seen their share prices soar since the invasion began, with German firm Rheinmetall up by more than 60% and Italy’s Leonardo up by more than 44%.

The highest-earning arms manufacturers raked in £300bn from sales in 2020 – twice the entire gross domestic product of Ukraine – according to the Stockholm International Peace Research Institute (SIPRI).

Samuel Perlo-Freeman, research coordinator for the Campaign Against Arms Trade, said: “War is good for no one but arms dealers.”

He added that BAE Systems, “like other major world arms companies, are seeing their share prices soar in response to the war on Ukraine, as European countries prepare to massively rearm, doubling down on the very militarism that has created so much death and suffering in Ukraine, Yemen and elsewhere.”

Tens of thousands of people are thought to have died in the conflict, including as many as 20,000 civilians in the besieged city of Mariupol in the south of the country. Last week, a Mariupol maternity hospital was shelled, killing a pregnant woman and her unborn child. And on Wednesday, Ukraine accused Russia of bombing a theatre in the city, where more than 1,000 people had been sheltering, including children.

Some executives at the biggest arms companies have already told investors that they are anticipating a rise in profits this year as a result of the war.

The CEO of US company Raytheon Technologies, the world’s second-biggest arms dealer, told an earnings call in January that the situation presented “opportunities for international sales”.

“The tensions in Eastern Europe, the tensions in the South China Sea, all of those things are putting pressure on some of the defence spending over there. So I fully expect we’re going to see some benefit from it,” he said in response to a question from an investor.

Arms companies have cheered the announcement by the German chancellor last month that the country will raise its spending on defence to 2% of its economic output. Germany had long resisted pressure from NATO allies to increase its military budget as public support for pacifism has remained strong.

The CEO of Rheinmetall, Armin Papperger, told the Financial Times: “Some months ago people wanted to ban us, to say that this industry is a very bad industry, a very harmful industry. It’s a totally different world now.”

Patrice Caine, CEO of French arms firm Thales, also told investors earlier this month that the news was “positive” for defence companies including his own.

Since the war began, governments across the world have pledged either to send arms to Ukraine or to increase their own spend on arms. The European Union has announced it will purchase and deliver €450m (£375m) of arms to Ukraine, while the US has offered $350m (£265m) in military aid.

The UK has sent 2,000 anti-tank weapons to Ukraine since Russia invaded and chancellor Rishi Sunak has faced calls to increase defence spending in his Spring Budget.

BAE Systems is already set to supply £3.4bn worth of munitions to the Ministry of Defence as part of a contract awarded in 2020.

When announcing its 2021 results last month, the company said that the “uncertain global environment” and “complex threats” facing the world would boost its business this year.

BAE Systems sold £24bn worth of arms in 2020, according to SIPRI. Last week, the UK firm sponsored an arms fair organised by the Saudi regime, where several sanctioned Russian state arms companies promoted weapons that have been used against Ukraine.

Roy Isbister, of the arms unit at 'peace-building' NGO Saferworld, said: “The war in Ukraine appears to be turbo-charging a vicious cycle where conflict leads to greater demand for arms, leads to heighten tensions, leads to further conflict, and so on. This cycle of violence ultimately benefits no one more than the arms companies and their shareholders, whose profits and prospects blossom as the bombs fall. There needs to be a fundamental rethink about the way we manage and prepare for international crises.”

Lord Glendonbrook, Lord Lupton, Lord Gadhia, Viscount Eccles and Lord Sassoon have been approached for comment.