Dallaglio: SA tour will test Lancaster
Before his role was made permanent, Lancaster steered England to four wins from five in this season's 6 Nations and in the process received strong backing and plaudits from his players.
But Dallaglio said: "South Africa is very tough and one of the hardest places to play rugby. I think when they come away from there they will know what they need to do both on a player perspective in terms of the squad but also a coaching perspective."
Lancaster's side will complete a three-test series against South Africa in June, with clashes against the Springboks in Durban, Johannesburg and Port Elizabeth.
Dallaglio, who led England during Sir Clive Woodward's reign, agrees the 42-year-old former RFU academy boss is the right man to take the side forward to the 2015 World Cup on home soil, but believes he still has to settle into the job.
"He certainly deserves the opportunity to continue in that role, there's no doubt about it," Dallaglio told Press Association Sport.
"His record from the 6 Nations shows how he has turned England's fortunes round in a very short space of time."
And Dallaglio, who was speaking as an Amlin Rugby Ambassador, is confident Lancaster has what it takes to succeed as a national coach despite not having a great deal of experience on the world stage.
"Coaching at the highest level is not normally down to one person, it's down to a number of factors," Dallaglio said. "Stuart and his team will know whether they need to add to that coaching staff at the end of the tour or if they've got enough themselves to do the job."