Willy Wimmer, who is a former MP for Mrs Merkel’s CDU party, said Germans want fresh leadership as Mrs Merkel struggles to form a government.
Mr Wimmer’s predictions follow a shock poll that shows Angela Merkel’s approval ratings have dramatically slumped over last three months.
The Chancellor has failed to strike a coalition deal since the election, which has left Germany without a government for 13 weeks.
She has since experienced a shock drop in public approval ratings, which will make her job of striking a deal more difficult, with talks planned in the new year.
A YouGov survey found that 47 percent of Germans surveyed want Merkel to step down before the end of her expected fourth term in office in 2021
On top of this, 36 percent wanted her to stay for the full tenure, a significant decline from 44 percent in October this year.
Mr Wimmer, the former deputy defence minister, told RT: “It was already a guess-on-guessing scenario – but this is the first step in having a change in the German government.
“Under German circumstances, it usually starts this way. The talks that start next year – even if successful – no-one expects it will last four years.
“This is a critical development. We have an economy that is flourishing and a political situation that is in change.”
Official discussions between the CDU and the SPD over a grand coalition are scheduled for 7th January.
However, the public’s belief in the forming of a new government is weak – with only 37 per cent of people expecting to have a new government before Easter.
According to the survey, 44 percent of people believe the difficulties in forming a government limit Germany’s ability to act in international politics.