Assuming you're using the default magento layout-

Open app/design/frontend/default/default/layout/catalogsearch.xml

< catalogsearch_result_index translate="label" > < reference name="root" > < action method="setTemplate" >< template >page/1column.phtml< /template >< /action > < / reference > </ catalogsearch_result_index>

Since you are not using Layer left block this will solve your issue.

Assuming you're using the default magento layout-

Open app/design/frontend/default/default/layout/catalogsearch.xml

<catalogsearch_result_index translate="label">
    <reference name="root" >
        <action method="setTemplate" >< template >page/1column.phtml< /template ></action>
    </reference>
</catalogsearch_result_index>

Since you are not using Layer left block this will solve your issue.