Britain will make a formal protest to the Ecuadorian government over its decision to provide asylum to WikiLeaks founder Julian Assange.

It comes as Swedish prosecutors dropped investigations into allegations of sexual assault against Assange after they ran out of time to bring charges.

Assange has been holed up at Ecuador's London embassy since 2012 to avoid extradition to Sweden.

In a statement, British foreign office minister Hugo Swire said Ecuador had helped Assange circumvent the law.

"Ecuador must recognise that its decision to harbour Mr Assange more than three years ago has prevented the proper course of justice," he said.

Swedish prosecutors dropped two of four allegations made in 2010 after reaching their statute of limitations of five years.

The accusations dropped involve one count of sexual assault and another of unlawful coercion. A separate allegation of sexual molestation will run out on August 18.

Swedish prosecutors said they would push on with an investigation into an allegation of rape made in 2010 against Assange as the alleged offence carries a 10-year statute of limitations and expires in 2020.

Under Swedish law, if a suspect is not questioned before the deadline expires, they can no longer be tried for the alleged crimes.

Assange has always denied the allegations brought by two Swedish women and insists the sexual encounters were consensual.

Ecuador said on Thursday that Sweden and Britain's "inaction" was to blame for the expiration of the Swedish sexual assault probe of Assange.

Ecuador's foreign ministry said in a statement "the continued inaction by British and Swedish authorities for the nearly 1,000 days of (Assange's) stay in the embassy" was the reason he had not been questioned by Swedish prosecutors.



Assange not 'playing the clock' on charges: lawyer

Despite repeated attempts, prosecutors have been unable to gain access to Ecuador's embassy.

They initially insisted Assange return to Sweden for interrogation, but he declined to return due to fears Stockholm could deliver him to US authorities, who may try him for leaking nearly 750,000 classified military and diplomatic documents in 2010.

In March, prosecutors agreed to Assange's compromise offer to question him inside the London mission, but said they had yet to see their request approved by Ecuador because of procedural issues, leading critics to suspect him of playing the clock.

Attorneys for Assange said suspicions that Ecuador was using delaying tactics were unfounded.

"The [Swedish] request came in late and is being processed by Ecuador, which will certainly approve it after following its own procedures," Assange's Swedish lawyer Per Samuelsson said earlier this month.

Claes Borgstrom, a lawyer for one of the two women accusing Assange of having assaulted them in 2010, said his client was trying to come to terms with the likelihood the case will never be tried.

"She has always been ready to stand by her accusations and wanted to bring the case to court," he said.

"But at the same time, a weight has been lifted. This has been dragging on for five years and she wants to go back to her normal life."

Assange is subject to a European arrest warrant and Britain has vowed to detain him if he sets foot outside the embassy, which is under constant police surveillance.

Reuters/AFP