**Exhibit 31.1**

**CERTIFICATION**

I,John J. McDonnell, Jr., certify that:

1.           I have reviewed this quarterly reporton Form 10-Q of TNS, Inc.;

2.           Based on my knowledge, this reportdoes not contain any untrue statement of a material fact or omit to state amaterial fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading withrespect to the period covered by this report;

3.           Based on my knowledge, the financialstatements, and other financial information included in this report, fairlypresent in all material respects the financial condition, results of operationsand cash flows of the registrant as of, and for, the periods presented in thisreport;

4.           The registrant’s other certifyingofficer(s) and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange ActRules 13a-15e and 15d-15e) and internal control over financial reporting(as defined in Exchange Act Rules 13a-15f and 15d-15f) for the registrantand have:

a.          Designed suchdisclosure controls and procedures, or caused such disclosure controls andprocedures to be designed under our supervision, to ensure that materialinformation relating to the registrant, including its consolidated subsidiaries,is made known to us by others within those entities, particularly during theperiod in which this report is being prepared;

b.         Designed such internalcontrol over financial reporting, or caused such internal control overfinancial reporting to be designed under our supervision, to provide reasonableassurance regarding the reliability of financing reporting and the preparationof financial statements for external purposes in accordance with generallyaccepted accounting principles.

c.          Evaluated theeffectiveness of the registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by thisreport based on such evaluation; and

d.         Disclosed in thisreport any change in the registrant’s internal control over financial reportingthat occurred during the registrant’s most recent fiscal quarter (theregistrant’s fourth fiscal quarter in the case of an annual report) that has materiallyaffected, or is reasonable likely to materially affect, the registrant’sinternal control over financial reporting; and

5.           The registrant’s other certifyingofficer(s) and I have disclosed, based on our most recent evaluation ofinternal control over financial reporting, to the registrant’s auditors and theaudit committee of registrant’s board of directors (or persons performing theequivalent functions):

a.          All significantdeficiencies and material weaknesses in the design or operation of internalcontrols over financial reporting which are reasonable likely to adverselyaffect the registrant’s ability to record, process, summarize and reportfinancial information; and

b.         Any fraud, whether ornot material, that involves management or other employees who have asignificant role in the registrant’s internal control over financial reporting.

DATE:August 9, 2006
|  /s/ JOHN J. MCDONNELL, JR.      |   |
|---------------------------------------|--------|
| John J.  McDonnell, Jr.          |
| Chairman and  Chief Executive Officer |

 

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