* Deadlines: draft constitution by end-April, vote by Dec
* Investors seek way out of crisis in cradle of Arab Spring
By Tarek Amara
TUNIS, March 15 (Reuters) - Tunisian lawmakers voted on Friday to have a draft constitution ready by the end of April and hold elections by December at the latest, steps meant to rescue a faltering democratic transition in the country that launched the Arab Spring.
The agreed timeline could ease tensions festering since the Feb. 6 assassination by suspected radical Islamists of secular opposition leader Chokri Belaid, and encourage local and foreign investors needed to hoist Tunisia out of economic crisis.
Mustafa Ben Jaafar, speaker of the constituent assembly, said the draft should be ready on April 27 - with July 8 as a final, fallback deadline if needed - with the next election to follow between Oct. 15 and Dec. 15.
Deputies voted 81-21 in favour of the timeline. An as-yet unformed supreme electoral commission will have the final word on the date for Tunisians to go to the polls.
"Agreement on these (dates) is an important message to both inside and outside the country ... that we are on the verge of completing the last stages of the democratic transition and going on to the stage of democratic stability," Moufdi Mssidi, Ben Jaafar's spokesman, told Reuters.
Feuding Islamist and secular politicians have missed previous deadlines to draw up a democratic constitution and set dates for parliamentary and presidential elections.
Belaid's murder ignited the worst violence in Tunisia since the January 2011 fall of autocratic President Zine al-Abidine Ben Ali to a mass uprising that inspired revolts against repressive leaders across the Arab world.
The North African state's new Islamist-led government won a confidence vote on Wednesday as the death of an unemployed man who set himself on fire in despair over economic hardships underscored the depth of popular discontent.
The government was broadened to include non-party independents in major cabinet posts to defuse outrage over Belaid's assassination.
Despite freedom of expression and political pluralism won in 2011, the high unemployment, inflation and perceptions of out-of-touch, corrupt government that fuelled the anti-Ben Ali revolt remain unresolved and often kindle further unrest. (Reporting By Tarek Amara; Editing by Mark Heinrich)