Rajapaksa made the remarks while addressing a two-day resident workshop for ambassadors, high commissioners and consul generals in the hill country resort of Diyatalawa.
The President said that Lankan envoys must be aware that LTTE diaspora with the help of their sympathisers are in a relentless campaign to discredit Sri Lanka.
The diaspora interact with policy makers, media and non governmental organisations to carry out their misinformation and hence the Lankan envoys must overcome this challenge, Rajapaksa stressed.
He called on the diplomats to effectively counter the adverse publicity against Sri Lanka by inventing suitable campaigns.
The President said Sri Lanka's foreign service had failed to highlight the high economic growth of 22 per cent achieved in the island's northern province since the end of the conflict three years ago.
This high growth in the north came when Sri Lanka achieved overall economic growth of 8 per cent.
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Rajapaksa said with his government's emphasis in developing the north, the other provinces came to be neglected.
Rajapaksa said Sri Lanka would continue to pursue its non aligned foreign policy.
"But foreign policy makers need to realise the importance of fostering further ties with the Asian region. Even the West now engages more with Asia due to its economic emergence", the president said.
The workshop was organised with the intent of revamping Sri Lanka's diplomatic offensive against the pro-LTTE campaign mainly in the West.
The island has faced international action such as the appointment of a special panel by the UN Secretary General to probe the alleged human rights violations during the three year battle which crushed the LTTE.
In March, the UN Human Rights Council adopted a resolution calling for human rights accountability measures.