The government has officially launched an investigation into the sale of stakes in the Independent and the Evening Standard to an investor with strong links to Saudi Arabia.

The culture secretary, Jeremy Wright, has ordered the competition and media regulators to investigate the sale of 30% holdings in the newspapers by Russian owner Evgeny Lebedev.

In December, Lebedev sold 30% of Lebedev Holdings to a Saudi businessman with ties to the country’s state-owned bank for £25m. In 2017, Lebedev sold a stake in the digital-only Independent to the same Saudi businessman.

Wright has launched a public interest intervention notice after failing to be persuaded by Lebedev’s guarantees that editorial independence will not be compromised.

“I continue to believe that it may be the case that the public interest considerations of freedom of expression and accurate news reporting are relevant to this merger,” said Wright, in a written ministerial statement on Thursday. “I thus consider it appropriate for me to intervene in this matter.”

Wright has asked the Competition and Markets Authority and Ofcom to conduct investigations and report their findings by 23 August. Earlier this month Wright had said he was “minded” to launch the investigation. At the time ESI Media, which operates both titles, said that it has “nothing to fear” from an investigation but that it would be an “unnecessary and expensive distraction”.

Any block on the investment could be an existential threat to the Evening Standard, which is edited by former chancellor George Osborne. In financial filings published on Wednesday it emerged that the London paper made a pre-tax loss of £11.5m last year, taking total losses to more than £23m in the last two years. Earlier this month the newspaper cut about 20 staff as part of a cost-cutting merger of print and online operations.

The Independent, which closed its print editions in 2016, made a pre-tax profit of £3m last year. Last year, The Independent joined up with the Saudi Research and Marketing Group, an arm of the Saudi government led by Mohammed bin Salman, to launch sites in Arabic, Urdu, Turkish and Persian.

“Our media outlets are firmly committed to the accurate presentation of news and freedom of expression,” said a spokesman. “Our editorial record speaks for itself. We uphold these values proudly, reflecting the trust the public places in us. We know that this trust is important – and all the more so in the current political climate. Our editorial policies, guidelines and reporting reflect these standards.”