Sir Philip Green’s retail empire faces a crunch meeting with creditors this week as it tries to avert a collapse into administration which could put 18,000 jobs at risk.

The group, which operates 570 shops, must win approval from 75% of its creditors, most of whom are landlords, for a restructuring which will enable it to close at least 23 stores and cut rents by up to 70% on nearly 200 more.

A further 25 UK stores are set to close as Arcadia puts the property holding companies of Miss Selfridge and Evans into administration. It is also closing 11 Topshop stores in the US.

The deal, which will be subject to a vote on Wednesday, also relies on reaching an agreement with the Pensions Regulator over funding of Arcadia’s pension deficit, which is valued at up to £750m.

The regulator, which has legal powers to force Arcadia and Green to ensure its pension is properly funded, wants a further £50m on top of the £360m over three years that has been put on the table.

Arcadia’s future will be decided as Green faces a new personal battle, after being charged with four counts of misdemeanour assault in the US, after a pilates instructor alleged he repeatedly touched her inappropriately, according to authorities in Arizona.

Pima County’s deputy county attorney, Lauren Deakin, said the Arcadia boss had been formally charged with four counts of “knowingly touching another person with the intent to injure, insult, or provoke”. Green denies the claims.

Each charge carries a potential sentence of up to 30 days in the Pima County jail, a fine of not more than $500, and up to one year of probation.

A Topshop store on Oxford Street, London. Arcadia is expected to close a number of the group’s outlets. Photograph: Luke MacGregor/Bloomberg

Green, who has not been in the UK since October, is due to appear in court in Tucson on 19 June, according to court filings.

In a bid to reassure Arcadia employees about their future, chief executive Ian Grabiner told staff in an email seen by the Observer that the management team had a “clear plan in place” to take on increased competition from both high street and online rivals backed by £135m of investment.

This includes £75m on a new hi- tech distribution centre in Daventry and a step up in wholesale sales, including taking Topshop onto fashion retailer Asos’s online platform for the first time. The company has also pledged £60m to upgrade its online operations.

Sofie Willmott, senior retail analyst at GlobalData, said the online investment was badly needed to ensure Topshop kept pace with the latest search tools and delivery options that many of its peers already offered. “It will now be even more important that the brands’ websites stand up to Asos’s best-in-class proposition,” she said.

In the email, Grabiner said: “I am confident that we can succeed in securing the future of the business but it is dependent on the backing of our landlords, the pension trustees, the Pension Protection Fund and the [Pensions Regulator].”

The proposal for Arcadia’s restructuring, an insolvency procedure known as a company voluntary arrangement (CVA), sets out the parlous state Arcadia finds itself in. The group was making nearly £220m in underlying profits three years ago.

In the document, Arcadia says it can no longer afford its £170m annual rent bill for its leased stores. Despite slashing £70m from its cost base in the last two years, it said it was not able to resolve its “significant financial difficulties”.

If the CVA does not go ahead, Arcadia has said it is “highly likely, either immediately or after a short time period, to enter into insolvent administration or liquidation”.

More than one landlord told the Observer they had yet to decide whether they would back the CVA.

Green has promised landlords a 20% stake in the business and a £40m compensation fund in an effort to secure their backing.

He also pledged to make a £50m cash investment in updating stores and online sales infrastructure at Arcadia – a sum which underpins the group’s £135m turnaround plan.