A British museum is resisting attempts from Canada to secure the repatriation of sacred relics of a 19th-century indigenous chief because the centre where his descendants want to locate them is not an accredited museum, but the final decision lies with local councillors in England.

In an increasingly acrimonious dispute, backers of the campaign to repatriate regalia belonging to Crowfoot of the Blackfoot Nation were told by officials at the Royal Albert Memorial Museum (RAMM) in Exeter that “no one wants to get their hands dirty” when it came to the sensitive question of repatriating looted artefacts held in UK arts institutions.

The resistance to attempts at repatriating items belonging to Crowfoot, who signed an 1877 treaty with crown forces, has demoralised those at a Blackfoot-run cultural and educational centre near to where he is buried, and which first lodged a formal repatriation request in 2015.

Facebook Twitter Pinterest UK museum sector does not have agreed protocol for dealing with repatriation requests for items like this Blackfoot beaded pouch. Photograph: Royal Albert Memorial Museum & Art Gallery

“We are currently in our second decade of repatriation efforts, with no end in sight,” the Guardian was told by Stephen Yellow Old Woman, general manager of Blackfoot Crossing Historical Park (BCHP). The centre has a purpose-built room ready to house the relics, which RAMM purchased for £10 in 1904 from the family of Cecil Denny, an English-born member of the Canadian mounted police, who was one of the signatories of the treaty with Crowfoot.

“It is like Siksika and Crowfoot are currently in a long dark tunnel with no end in sight,” added Yellow Old Woman, who dates the beginning of the repatriation initiative back to 2008.

The impasse over the return of the sacred indigenous relics comes as the Arts Council has tendered for help in drawing up new guidelines aimed at reshaping the British museum sector’s wider approach to repatriation requests after European countries including France and Germany have committed to handing back objects.

Multiple disputes over items in British museums include west African treasures plundered by British forces, from the Parthenon marbles at the British Museum, a long-running focus of Greek demands, and more recent requests by Gibraltar for the return of Neanderthal remains.

Efforts to repatriate the Blackfoot regalia, which ranges from Crowfoot’s cream-hued buckskin shirt and leggings to a dee hide necklace strung with grizzly bear claws, have been backed by Alberta’s provincial premier, Jason Kenney. Canada’s Globe and Mail reported that he had written to British officials to say that the repatriation “would be regarded as a great act of reconciliation with Canada’s indigenous people”.

However, RAMM officials told the Blackfoot historical party that the letter from the premier “has no effect whatsoever on how we operate here in the UK”.

This reply was “just the tip of the iceberg”, said Yellow Old Woman, who added: “Much of this whole experience has been shocking to us.”

In a document shared with the Guardian, RAMM said the BCHP was not accredited with the Canadian Museums Association and that details needed to be provided about the long-term preservation of returned materials. Details about governance had also been requested “to minimise the risk of competing or conflicting claims for the same material” but negotiations had stalled because not all of the information had been sent by the BCHP.

RAMM has now written directly to the Siksika tribal council, elected representatives of the Siksika nation and part of the Blackfoot confederacy, proposing that the repatriation request is considered by Exeter city council’s executive committee in June. The letter also asked for information on the governance relationship between BCHP and the tribal council, plus sought clarification about who would have future ownership of the regalia.

It added: “In recent months, debates on decolonising Britain’s museums have intensified. The response of UK museums has been disparate, ranging from examples of unconditional repatriations to a lack of engagement with indigenous communities.”

The UK museum sector does not have a single, agreed protocol for dealing with repatriation requests, it added, and RAMM is currently reviewing its own process of dealing with such requests.