Kate and Gerry McCann were left furious after the former detective delayed their libel action by making a last-minute application to remove powers from his lawyer on the day they were due to deliver personal statements about the effect allegations in his book had had on them.
Mr and Mrs McCann had travelled to Lisbon on what was due to be the last day in the trial at the Palace of Justice, Lisbon, but will now have to return on July 8 after Mr Amaral's 11th-hour application prompted the latest delay in the long-running case.
The obviously-angry and upset couple branded the delay - made by Mr Amaral at 9am yesterday - a "blatant and cynical attempt" to wear them down.
Speaking outside the court in Lisbon, Glasgow-born Mr McCann said: "We're exasperated the hearing has been cancelled once again at Mr Amaral's request. This is the fourth time this has happened and we've travelled to Portugal.
"The legal case has been running now for over five years and we want to get justice for Madeleine.
"Today is a blatant and cynical attempt to wear us down and it's Madeleine who is suffering.
"We're not going to give up - we're going to keep going."
The McCanns are suing for libel over claims made in Mr Amaral's 2008 book The Truth Of The Lie, including suggestions they hid Madeleine's body after she died in an accident and faked an abduction, saying the claims damaged the hunt for their daughter and exacerbated their anguish.
If successful, the family stands to gain about £1 million in damages.
The latest stumbling block in their legal battle came as Mr Amaral made more outlandish claims about Madeleine's disappearance in an interview with a Portuguese and its sister TV channel CMTV.
Addressing journalists outside court, a visibly-upset Mrs McCann said every delay to the libel case brought more "pain and distress" to the family.
She said: "We need to make it clear to people: we took on this case because of the pain and distress Mr Amaral has brought to us and our children. And every time he postpones the case like this, it brings us more pain and distress.
"Every time we come here, we have to make arrangements for our children to be looked after, we have to book flights, we have to book hotels, we have to take time off work to come here.
"And Mr Amaral handed that letter in apparently around nine o'clock this morning. That letter could have been handed in before we left the country.
"And this has happened about four times. We just want justice. This is not fair."
The McCanns' return to Portugal comes after they said last week that because police found no evidence relating to their missing daughter during recent searches in Praia da Luz it had reinforced their belief she could still be alive.
Madeleine, who was then nearly four, disappeared from her family's holiday apartment in Praia da Luz, Algarve, on May 3, 2007 as her parents dined at a nearby restaurant with friends.
Asked whether he thought Madeleine was alive, Mr McCann said: "What is clear is that the searches haven't found any evidence to show Madeleine has been seriously injured or is dead.
"As far as we are concerned, there is a good chance she is still alive and we have to keep searching for her - that's why we are here."
He added: "What's absolutely clear is Madeleine is completely innocent in all this. This is what it's about. An innocent child is missing."
Mr McCann, asked if he had any message for Mr Amaral, said curtly: "We are not speaking to Mr Amaral."
Vitor Santos de Oliveira, who had been the lawyer for Mr Amaral, said he learned of the former detective's decision on Sunday night. Asked if he knew why, he said: "These are decisions that people make. If I knew why, I would say."