Newcastle Falcons will stay in the top flight of English rugby union next season, regardless of whether London Welsh win promotion later this month, the Rugby Football Union said on Wednesday.
London Welsh, one of the top clubs of the 1970s, are due to play the second leg of the Championship final on May 30, victory in which would ordinarily see them go up to the Premiership at the expense of the northeast club, who finished bottom.
But the RFU appointed independent auditors to assess whether London Welsh's ground was suitable for the league.
"The report, carried out by independent auditors, found that London Welsh has not met the MSC (minimum standards criteria) for the Premiership," the RFU said in a statement.
"The independent auditors identified various failures, including not having Primacy of Tenure at their nominated ground (English football League Two side Oxford United's Kassam Stadium).
"This states that a club must demonstrate that they can host home fixtures at the time stipulated by Premiership Rugby and/or the host broadcaster.
"The RFU Board ratified the findings and agreed, should London Welsh win the RFU Championship final following the second leg on May 30, they would not be eligible for promotion and Newcastle Falcons would remain in the Aviva Premiership."
However, London Welsh later hit back with a strongly worded statement, though, they stopped short of saying whether they would appeal as they have 14 days to do so.
"London Welsh RFC would like to express its grave disappointment on learning of this decision coming as it does just a few hours ahead of the first leg of the club's Championship Final against the Cornish Pirates.
"The Club firmly believes that it has met the Minimum Standards Criteria (MSC) for promotion to the Premiership, particularly as regards the issue of Primacy of Tenure and reaffirmed its belief in this respect in a detailed communication to the RFU as recently as Monday 21st May highlighting its case for having satisfied the MSC."
London Welsh's Championship final opponents Cornish Pirates have chosen not to have an independent audit of their Mennaye Field ground, so are also ineligible for promotion.
No Championship side, therefore, will go up this season, the RFU said.