The appeal is the charity's biggest ever coastal fundraiser and will help ensure that public access to the White Cliffs can be improved for future generations to enjoy.
It will also mean that the much-loved stretch of Kent coastline can be cared for in a way that will improve its habitat for local wildlife.
If the appeal is successful, the most iconic stretch of the White Cliffs - the 1.35km (just under one mile) sweep overlooking the port of Dover - will be looked after and managed for the benefit of the public and for wildlife.
It will complete the missing link of coastline under National Trust care, uniting a stretch of more than 7km (nearly 5 miles) between the Trust's visitor centre and South Foreland lighthouse.
Hilary McGrady, Director for the South East at the National Trust, said: "Immortalised in song and literature, the White Cliffs of Dover have become one the great symbols of our nation.
"We now have a once in a lifetime opportunity to secure their future for everyone to enjoy.
"If we don't raise the money then the future of the White Cliffs is uncertain and this stretch of coastline might one day be disrupted by inappropriate management or development."
Standing proud at over 110 metres (taller than Big Ben or the same height as twenty-five London buses stacked on top of each other), the White Cliffs of Dover have witnessed many dramatic moments in England's history.
These include the arrival of the Romans and the welcome return of British armed forces after the evacuation of Dunkirk during the second-world war.
The cliffs are also home to a rich array of rich wildlife including the Adonis blue butterfly, rare coastal plants such as oxtongue broomrape and sea carrot, and birds including skylark, the only colony of Kittiwakes in Kent and peregrine falcons.
Historian and television presenter Dan Snow, who is supporting the appeal, added: "For me it's simple. The White Cliffs of Dover are one of the country's greatest and most iconic landmarks.
"When I heard that the National Trust had this opportunity to safeguard this crucial stretch of the Cliffs, I thought great.
"It's brilliant that they have a chance to secure this important section of the cliffs, for ever, for everyone."
Across England, Wales and Northern Ireland the National Trust looks after more than 720 miles of coastline. The Trust acquired its first stretch of the White Cliffs of Dover in 1968.
Hundreds of thousands of people come to visit the dramatic chalk cliffs every year with their wonderful views across the English Channel.
The funds need to be raised by the end of the year to help acquire this piece of the Kent coast and help with the conservation and management of the White Cliffs of Dover.
There are three ways that money can be donated to the appeal:
- Make a donation online at www.nationaltrust.org.uk/whitecliffsappeal and you can choose to have your name engraved on their virtual White Cliffs of Dover.
- You can text a donation to support the appeal. For example, if you wanted to donate £5 you'd need to text 'DOVR02 £5' to '70070'. The amount that you wish to donate must be included in the text.
- Make a donation over the phone by calling 0844 800 1895.
The Twitter hashtag #whitecliffs will be used on twitter to keep people updated about the progress of the appeal.
