England reached 12 successive Test wins when it thumped Wales in the first round in February. But it lost its remaining four games, including an historic first defeat to Italy, and finished fifth.
Borthwick's team was guilty of indiscipline, over-kicking and not being clinical. After four Six Nations under Borthwick, England has yet to win in Scotland, Ireland or France.
The England Rugby Football Union wouldn't detail the team's issues because of "performance confidentiality in a competitive sporting environment" but chief executive Bill Sweeney said an unnamed panel of rugby figures undertook a "thorough and honest review."
"This is a young England team that is still growing and developing, and we understand progress in international sport is rarely linear," Sweeney said.
"Steve has engaged in this process with full openness and has clear plans in place to address these findings.
"We are all behind him and his coaching team going into the Nations Championship and the series of matches leading into Rugby World Cup 2027."
The RFU said Borthwick was given credit for the 12-match, year-long winning run.
"England's underperformance across the Six Nations was not the result of a singular failure or issue," it said.
"Instead, it highlighted a number of interconnected performance areas, such as discipline, execution of opportunities and making the most of key moments, where improvement is required if England are to consistently perform at the level expected.
"(Borthwick) and his coaching team are already addressing issues identified."
England's next match is against world champion South Africa in Johannesburg on July 4 in the Nations Championship.
The World Cup in Australia is in 17 months.
16°C